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31 featured content items: Featured articles (30) H, He, O, F, Zn, Ge, Y, Nb, Tc, Xe, Cs, Pb, At, Fr, Th, U, Pu, Cf, Db, Hs, Nh, Ts, Og, noble gas, metalloid, periodic table, heavy metals, radiocarbon dating, history of aluminium, island of stability Featured topics (1) period 1 elements Signpost interviews: 2011, 2013 view edit Detailed list Article quality in the periodic table Other high-quality articles

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This is based on gas phase electron configurations. There is a lot going on here. There are two images as I couldn't get the whole thing onto one screen with sufficient resolution. Every time I worked on it there was something else needing fixing. I hope I have it right now. @Double sharp: I'd be especially grateful for any thoughts on the An and super-heavies as far as whether I got them right. Our articles on these elements have been so helpful. Sandbh (talk) 08:14, 5 July 2020 (UTC)[reply] @Sandbh: As we can see strongly from this, the waves thrusting the gas-phase configurations here and there don't strongly result in anything consistent. In the d-block we can see lots of almost totally identical pairs like Nb-Ta and Mo-W which seem to not care at all about having different gas-phase configurations. And likewise in the f-block we see extremely different pairs like Sm-Pu with the same configuration. And compare both to the not very good resemblances Sn-Pb and Sb-Bi. ^_^ Note that this table clearly shows the superiority of Lu under Y, in avoiding Lu and Lr hanging around in the f block past the fully filled subshell and with no possibility of using their f electrons for chemistry. Critique of all notes: A. If we are allowing predictions, note that caesium is predicted to do much the same under pressure, acting like a seventh 5p element after Xe. In fact there have even been some vague experimental indications that it may be possible to get the Cs3+ even without the pressure (Greenwood and Earnshaw, p. 83), though nothing confirmed yet. B. Two points for this one. B.1. If you look at 2nd, 3rd, 4th IEs you can easily get high numbers that don't actually make sense with periodicity. The alkali metals will surely get you very high numbers for all of that. You have to instead look at what you're doing. Outside the transition metals, the first IE makes by far the most sense, as that is going straight from the neutral configuration, so you can immediately see where the half- and fully-filled shells are. Indeed, you get a peak at nitrogen and a fall to oxygen, that's perfect. Notice that you do not get this peak going from antimony to tellurium, in keeping with the trend that this effect diminishes for later and later periods. For transition metals (d and f blocks), then the third one makes more sense because usually the s electrons go first before the d and f ones go. B.2. Saying "low EA" are seen for Gd-Cm is rather missing the point. Here are the values for the f elements in kJ/mol: La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb 54 55 11 9 12 16 11 13 13 ≥34 33 30 99 0 Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No 34 113 53 51 46 0 10 27 0 0 0 34 94 0 Of course, you know what I think of negative EA. That's why I put zeroes instead of those negative numbers. But even if you don't, I think it's fairly obvious that you really cannot single out Eu-Am or Gd-Cm as being especially "low" alone. Tb is about the same as Gd, Bk is zero unlike positive Cm. So? The only thing we can consistently say here seems to be that as usual the zero value happens at the end of the block. As usual this is broken by gatecrasher Lu in the La table, even if not by Lr for once. C. What "dip" for tellurium? If you actually plotted it you'd find that the dip shrinks in each period until it goes away (continuum again). Terbium 1st IE is irrelevant to its position, see B.1. The relevant 3rd IE shows the expected strong dip at gadolinium. D. Yet again the 1st IE is irrelevant for these elements, you want the 3rd one. (Of course it should be noted that La and Ac in the d-block look like clear outliers.) E. Probably roentgenium will not form the −1 state. Predicted EA is closer to silver (which doesn't) than gold (which does). F. That's not its real electronegativity, that's because of cluster formation. Au is similarly overestimated by Pauling. G. and H. OK. I. and J. It's not "inaccessible". 1s in He is no problem to involve itself in bonding in charged compounds like HeH+, same thing for Ne 2p and Ar 3p. Neutral compounds are the problem. K. OK. L. I don't know if this means much of anything looking at the weirdness in the f-block (see point B.2). M. It's not "inaccessible" either. 3d contributes to the bonding in ZnF2, as previously presented here with sources. It's part of the valence MOs. N. See B.2. O. Correct. And a good sign that they are not f-block elements at all, since the f subshell is to the contrary accessible in La, Ac, and Th. P.1. The exact same thing has happened for La and Ac. Both have some delocalisation into the f subshell which overlaps the other valence bands and indeed they both have the "wrong" crystal structure for the group 3 column. Of course for this one it is just adding fuel to the fire with increasing d occupation in the metal as the atom gets bigger, but f participation and occupancy also is concurrently getting bigger (see Gschneidner) and is responsible for high coordination numbers and low melting points. P.2. ThIII in chemical environments is almost always 6d1, not 5f1. Double sharp (talk) 04:31, 6 July 2020 (UTC)[reply]

I would readily describe this PT as not being "groupic", but I would not say the same about "our" enwiki PT. (See special:diff/973773980) YBG (talk) 05:40, 1 September 2020 (UTC)[reply]

…via symmetry breaking

^ see

Table updated Sandbh (talk) 12:21, 23 August 2020 (UTC)[reply]

--- Sandbh (talk) 07:31, 22 July 2020 (UTC)[reply]

If you cannot make a legible statement, Sandbh, then remove this post yourself please. -DePiep (talk) 00:24, 25 July 2020 (UTC)[reply]

Regularity and symmetry

It's curious that interest in the regularity and symmetry of periodic system representations has some basis in Z and the Madelung Rule. Yet the MR sort of has some bumps in it, and there was the early crisis of confidence in the periodic table when the old school physicists and chemists had to grapple with what to do with isotopes of the elements. Having accommodated that, it turns out the periodic law is only an approximation, rather than a Law, as such. That leads into the observation that there is no ideal periodic table, since the table depends on the properties of interest. Hence Tier 5. From the perfection of Tier 1, we descend into the "chaos" of Tier 5.

Thus, an emerging field of thought is the importance of symmetry breaking, rather than pure symmetry:

1. "…symmetries matter, largely because we like to see them broken sometimes: the laws, particles and forces of physics all have their roots in symmetry-breaking. They create what David Gross of the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara, calls the "texture of the world". These considerations have led Florian Goertz at the Max Planck Institute for Particle and Astroparticle Physics in Heidelberg to propose the existence of a new particle that is single-handedly capable of cleaning up five of the stickiest problems in physics. "Complete symmetry is boring," says Goertz. "If symmetry is slightly broken, interesting things can happen." " (Brooks 2018, p. 30)

2. "Through the work of many physicists, the concept of broken symmetry was introduced into elementary particle physics in the 1960s and 1970s. The idea was, in the simplest language, to keep the mathematical forms symmetrical, but the physical consequence unsymmetrical. The standard model, for which Glashow, Salam, and Weinberg shared the Nobel prize in 1979, was based on gauge theory with broken symmetry. It has been extremely successful." (Yang 1996, p. 286)

3. "Physical chemistry is fundamentally asymmetric. How could it not be when the proton weighs so much more than the electron?" (Philip Stewart, pers. comm. 30 Dec 2019).

Evidence of new physics could have been under our noses all along

4. "Many of these remaining problems boil down to one. Crudely phrased, some things are exceptionally small while related things are exceptionally big. This is known as the hierarchy problem, and once you spot it, you start seeing it everywhere.

Take the four fundamental forces of nature. The weakest two are gravity, and the weak nuclear force, which only operates on the tiniest of scales and is responsible for certain types of radioactive decay. The weak force is weak, but compared with it, gravity is some 25 orders of magnitude weaker – a bizarre state of affairs that, as yet, has no good explanation.

The asymmetry reappears elsewhere. Dark energy, the mysterious force that is causing the universe’s expansion to accelerate, is 120 orders of magnitude weaker than we would expect. Dark matter, which is the dominant form of matter in the universe, interacts very weakly with regular matter. Neutrinos, the lightest particles in the standard model, are thousands of times lighter than anything else.

These disparities are profoundly vexing to physicists, who prefer to see related parameters in a theory take broadly consistent values. This preference for "naturalness" drives much theoretical speculation – some would say to a fault. "Nature doesn’t care about our aesthetics," says [Nathaniel] Craig [a theoretical physicist at the University of California, Santa Barbara].

Ten years on, nothing has changed. We were fixated on supersymmetry for too long, says Isabel Garcia at the University of California, Santa Barbara, searching under the convenient street light to the detriment of the field. But the story of the LHC is far from over. The collider has recorded only 3 per cent of the data we expect it to collect in its lifetime, and an upgrade to higher energies in 2020 will further raise its chances of seeing something surprising.

But the LHC's failure to break any new ground has emboldened a new generation to question the hunches that motivated previous searches. "This optimism is most widespread amongst the youth," says Matthew McCullough, a theoretical physicist at CERN. "We've shaken off the cobwebs of the theories handed down by our PhD advisers." " (Eure 2019)

It remains to be seen if the YAPs (young asymmetrical pups) can teach the OSDs (old symmetrical dogs) some new tricks

Even so I consider that (a) asymmetry cannot be appreciated or understood without understanding (b) symmetry, and how and why things go from (b) to (a). See also Hegstrom & Kondepudi (1990), and Rosen (1996).

• Brooks, M.: This one particle could solve five mega-mysteries of physics. New Scientist, 3191, (2018)
• Eure, J. Evidence of new physics could have been under our noses all along. New Scientist, 3217, 16 Feb (2019)
• Hegstrom, R.A., Kondepudi, D.K.: The handedness of the universe. Sci. Am. 62, 108–115 (1990)
• Rosen, J.: Symmetry in science: An introduction to the general theory. Springer, New York (1996)
• Yang, C.N.: Symmetry and physics. Proceedings of the American Philosophical Society. 140, 267–288 (1996)

--- Sandbh (talk) 02:19, 25 July 2020 (UTC)[reply]

Four irregularities

Each of the four irregularities namely electrons; neutrons; element properties; and periodic systems has some kind of guided boundary.

This reinforces my impression that all periodic systems have their place under the sun. That is the key learning for students.

Null sub-section

Tier 2: Electrons

The Madelung Rule always returns to running true after each wobble (analogous to a gyroscope?).

Tier 3: Neutrons

Their numbers are bounded by the

Boeyens and Levenids (2008, p. 144) write:

"Harkins (1931) discovered a classification of the the stable nuclides in terms of the ratio N/P and showed that this ratio never exceeds the value of 0.62 in atomic species. The same classification was rediscovered independently many years later (Boeyens 2003) and the maximum was shown, more precisely, to be the golden ratio = 0.6180."

• Boeyens, JCA 2003, J. Radioanal. Nucl. Chem., 257, 33
• Boeyens JCA and Levendis DC 2008, Number theory and the periodicity of matter, Springer
• Harkins 1931, Phys. Rev., 38, 1270

Tier 4: Element irregularities

The irregularities in the properties of the elements might possibly be encompassed by the work of Hsueh and Chiang (1937). See appendix 2.

Chemically, the metallic or nonmetallic nature of the elements correlates with, to at least a first order approximation, the four key properties of

• atomic radius
• electron affinity
• ionization energy; and
• electronegativity.

On atomic radius, Peter Atkins (2019) wrote:

"The periodic table and the concept of the elements of education inspires all manner of other thoughts. One is the desert-island thought: if you were asked to identify the central elemental concept summarized by the periodic table which, with you isolated on a conceptual desert island and asked to set about rationalizing chemistry, what would it be? My choice would be atomic radius."

Here.

Godovikov & Hariya (1987) showed a relationship between atomic (orbital) radius and electron affinity:

Here.

Myers (1981) demonstrated a smooth curvilinear relation, for vertical groups in the periodic table, between the electron affinity of an atom and the ionization energy of its neighbour with atomic number larger by one:

Here.

I showed a correlation between EN and radius in my Constellation of electronegativity:

Here.

Thus:

Atomic radius	→	Electron affinity
↑		↓
Electro- negativity	←	Ionization energy

Tier 5: Periodic systems

I hope my periodic system landscape, based on the ideas of Scerri and Schwarz, represents a crude start to showing some semblance of order.

Appendix: Symmetry breaking

Much like a pencil falling to the ground from its tip in a trade-off of symmetry for stability, Davies (2007) writes that the Big Bang could have established a complex but stable universe (or multiverse) from symmetry breaking as the heat radiation in "space" lowered abruptly past the Curie Point.

Here.

Ethan Siegel, an astrophysicist, concludes:

"Our Universe may not be as elegant as we hoped for after all."

Here.

That said, there is a lot of order amongst the disorder. That seems to be the key: pure order = complete stasis; pure disorder = complete chaos. Interesting things happen between the two poles. As the Goldilocks principle goes, "Neither too much nor too little, but just right."

"When Coleridge tried to define beauty, he returned always to one deep thought; beauty, he said, is unity in variety! Science is nothing else than the search to discover unity in the wild variety of nature,—or, more exactly, in the variety of our experience. Poetry, painting, the arts are the same search, in Coleridge’s phrase, for unity in variety."

Bronowski J 2011, Science and human values, Faber & Faber, London

Appendix: Chin-Fang Hsueh and Ming-Chien Chiang

J. Chinese Chem. Soc, 5, 263 (1937). (In English)

I attempted to get a copy of this article via the Australian National Library, and the British Library Lending Service, without success. The Australian National University holds copies of the serial involved, but this particular volume was missing.

The article is cited in Moeller’s Inorganic chemistry (1953, p. 119) in the following passage:

"In an extremely interesting and searching article, Hsueh and Chiang consider any periodic property to consist of two factors, one a periodic factor determining the periodicity and the other an amplitude factor causing numerical change in the property within a given family of elements.

The periodicity factor is, in turn, a function of valency or outermost electronic configuration, and the amplitude factor is a function of energy state and atomic radius.

The periodicity function may be either a maximum at the center of a period or a minimum at the center.

Periodic properties of the increasing class embrace atomic frequency, melting point, boiling point, etc., whereas those of the decreasing class are atomic volume, atomic radius, atomic parachor, etc.

Correspondingly, the amplitude function may amount to either parallel or crossing combination, that is, the amplitudes for the sixteen periodic families may simultaneously increase or decrease or they may change in reverse order for positive and negative elements.

Properties involving parallel combination are such ones as atomic volume, atomic radius, ionic radius, and ionization potentials, whereas those involving crossing combination are such ones as melting point, boiling point, and hardness.

Periodic properties may therefore be classified, according to Hsueh and Chiang, into the four general types: parallel amplitude, increasing periodicity; parallel amplitude, decreasing periodicity; crossing amplitude, increasing periodicity; and crossing amplitude, decreasing periodicity.

By combining periodicity and amplitude functions, Hsueh and Chiang derive a property equation [to follow, Sandbh] from which the numerical magnitude of a property P is related to the atomic number Z of the element in question in terms of valence V, a function of the periodic factor y, the principal quantum number n, and two parameters a and p, which are constants for a given family of elements but different for different families.

By means of this equation and a consideration of the types of periodic properties already mentioned, theoretical variations in properties are evaluated and found to be in reasonably good agreement with observed variations. Certainly curves plotted from theoretical values so calculated against atomic number agree closely with similar ones drawn from measured values."

--- Sandbh (talk) 07:45, 26 July 2020 (UTC)[reply]

​​​​​I've been looking again at categorising the nonmetals.

We may discern: (a) H, C, N, O, P, S and Se; (b) the halogen nonmetals; and (c) the noble gases.

I'll set aside the noble gases.

The halogen nonmetals F, Cl, Br, and iodine are called that in recognition of their tendency to form "salts". The name "halogen" means "salt-producing". The etymology is Greek halo, ἅλς, ἁλο- salt; French -gène, ultimately representing Greek -γενής, γεν- root of γίγνεσθαι to be born, become, γεννάειν to beget, γένος kind, etc. Thus, from our halogen article: "When halogens react with metals, they produce a wide range of salts, including calcium fluoride, sodium chloride (common table salt), silver bromide and potassium iodide." The IUPAC Gold Book defines a salt as, "a chemical compound consisting of an assembly of cations and anions". Bear in mind that while the halogens tend to give rise to salts, they can also (less often) produce non-salts.

Now, when it comes to the type (a) nonmetals, they tend to form polymeric or covalent compounds, bearing in mind that (to a lesser extent) they can also produce salt-like compounds (the azides, for example). A little clarification about oxygen. Metal oxides are usually ionic. On the other hand, oxides as a whole, including the metalloids and nonmetals, are usually either polymeric or covalent. A polymeric oxide has a linked structure composed of multiple repeating units.

So, is there a word meaning either "non-salt" or "non-ionic compound", where non-ionic means polymeric or covalent?

"Coactive" means, "acting in concert; acting or taking place together". That seems like a good word wrt the covalent compounds of H, C, N, O, P, S and Se. For their polymeric compounds, e.g. of H, N, O or S, the connection is to the linked nature of their repeating structural units. Thus, there would be (1) "coactive nonmetals"; (2) halogen nonmetals; and (3) noble gases. That is how the literature tends to deal with the nonmetals, except that it has no common term for the first category.

Bear in mind the expression coactive nonmetals is not currently found in the literature. For me, that is not such a big issue given the schemozzle-like state of nonmetal categories in the literature, a topic which I revisit at the end of this contribution. If needs be, I could get it into the literature by way of a journal article. I already have an article in the literature

It’s memorable to see their dualistic Jekyll (#2) and Hyde (#4) behaviours. Sandbh (talk) 05:33, 31 July 2020 (UTC)[reply]

It's puzzling that, in the literature, the metals start out loud and proud, as alkali metals; alkaline earth metals; Ln/An; transition metals; and then fade away with the sixteen different names for the

H → C Chemical similarities between hydrogen and carbon, including the possible relocation of hydrogen to group 14, have been discussed (Cronyn 2003). They include comparable ionization energies, electron affinities and electronegativity values; half-filled valence shells; and correlations between the chemistry of H–H and C–H bonds.

H → C → N → P → S → O

H → N Both are relatively unreactive colourless diatomic gases, with comparably high ionization energies (1312.0 and 1402.3 kJ/mol), each having half-valence subshells, 1s and 2p respectively. Like the reactive azide N³⁻ anion, inter-electron repulsions in the H⁻ hydride anion (with its single nuclear charge) make ionic hydrides highly reactive. Unusually for nonmetals, the two elements are known in cationic forms. In water the H⁺ "cation" exists as an H₁₃O₆⁺ ion, with a delocalised proton in a central OHO group (Stoyanov et al. 2010). Nitrogen forms an N₅⁺ pentazenium cation; bulk quantities of the salt N₅⁺SbF₆⁻ can be prepared. Coincidentally, the NH₄⁺ ammonium cation behaves in many respects as an alkali metal anion (Rayner-Canham and Overton 2010 p. 265).

H → N → O Several hydroxo-nitrogen acids or there salts are known of composition H_xN_yO_z (x = 1–3; y = 1–2; z = 1–4). The best example is nitric acid HNO₃.

H → N → O → S Nitrosylsulfuric acid NOHSO₄ is a colourless solid that is used industrially in the production of caprolactam, a colourless solid with a lobal demand of about five million tons per year, the vast majority of which is used to make nylon filament, fiber, and plastics.

C → N With nitrogen, carbon forms an extensive series of nitride compounds including those with high N:C ratios, and with structures that are simple (CN₁₂); chain-like (C₆N₂ for example); graphitic (linked C₆N₇ units); fullerenic (C₄₈N₁₂) or polymeric (C₃N₃ units). Most of the compounds prepared to date also contain quantities of hydrogen (Miller et al. 2017).

C → P Carbon and phosphorus represent another example of a less-well known diagonal relationship, especially in organic chemistry. Spectacular evidence of this relationship was provided in 1987 with the synthesis of a ferrocene-like molecule in which six of the carbon atoms were replaced by phosphorus atoms (Bartsch et al. 1987). Further illustrating the theme is the extraordinary similarity between low-coordinate trivalent phosphorus compounds (in which phosphorous has less than three nearest neighbours) and unsaturated carbon compounds (in which carbon has at least one double bond, or a triple bond), and related research into organophosphorus chemistry (Rayner-Canham 2011; Dillon et al. 1998).

N → P Like nitrogen, the chemistry of phosphorus is that of the covalent bond; the two nonmetals rarely form anions. Despite them being in the same group, and the composition of some of their compounds resembling one another, the individual chemistries of nitrogen and phosphorus are very different (Wiberg et al. 2001, p. 686). That said, the two elements form an extensive series of phosphorus–nitrogen compounds having chain, ring and cage structures; the P–N repeat unit in these structures bears a strong resemblance to the S–N repeat unit found in the wide range of sulfur–nitrogen compounds, discussed next (Roy et al. 1994).

N → O Nitrogen and oxygen represent the main parts of air. They both become toxic under pressure thus, nitrogen narcosis; oxygen narcosis. They react readily with one another. Nitrogen forms several oxides, including nitrous oxide, N₂O, in which nitrogen is in the +1 oxidation state; nitric oxide, NO, in which it is in the +2 state; and nitrogen dioxide, NO₂, in which it is in the +4 state.

Many of the nitrogen oxides are extremely volatile; they are prime sources of pollution in the atmosphere. Nitrous oxide, also known as laughing gas, is sometimes used as an anaesthetic; when inhaled it produces mild hysteria. Nitric oxide reacts rapidly with oxygen to form brown nitrogen dioxide, an intermediate in the manufacture of nitric acid and a powerful oxidizing agent utilized in chemical processes and rocket fuels.

More generally nitrogen resembles oxygen with its high electronegativity and concomitant capability for hydrogen bonding and the ability to form coordination complexes by donating its lone pairs of electrons. There are some parallels between the chemistry of ammonia NH₃ and water H₂O. For example, the capacity of both compounds to be pronated to give NH₄⁺ and H₃O⁺ or deprotonated to give NH₂⁻ and OH⁻, with all of these able to be isolated in solid compounds.

N → S Nitrogen and sulfur have a diagonal relationship, manifested in like charge densities and electronegativities especially when sulfur is bonded to an electron-withdrawing group. The two elements are able to form an extensive series of seemingly interchangeable sulfur nitrides, the most famous of which, polymeric sulfur nitride, is metallic, and a superconductor below 0.26 K. The cyclic S₃N₂²⁺ cation, in particular, serves as an exemplar of the similarity of electronic energies between the two nonmetals (Rayner-Canham 2011, p. 126).

N → O → S Sulfur nitride oxide chain and ring compounds are known of composition S_xN_yO_z (x = 3,4,7,15; y = 2,4,5,6; z = 1,2,5,8).

O → S Oxygen and sulfur react readily with one another, forming lower sulfur oxides (S_nO, S₇O₂ and S₆O₂); sulfur monoxide (SO) and its dimer, disulfur dioxide (S₂O₂); sulfur dioxide (SO₂); sulfur trioxide (SO₃); higher sulfur oxides (SO₃ and SO₄ and polymeric condensates of them); and disulfur monoxide (S₂O). The burning of coal and/or petroleum by industry and power plants generates sulfur dioxide (SO₂) that reacts with atmospheric water and oxygen to produce sulfuric acid (H₂SO₄) and sulfurous acid (H₂SO₃). These acids are components of acid rain, lowering the pH of soil and freshwater bodies, sometimes resulting in substantial damage to the environment and chemical weathering of statues and structures. In most oxygen-containing organic molecules, the oxygen atoms can be replaced by sulfur atoms.

P → S (Se) Phosphorus reacts with sulfur and selenium (and oxygen) to form a large number of compounds. These compounds are characterized by structural analogies derived from the white phosphorus P₄ tetrahedron (Monteil and Vincent 1976).

S → Se Commonalties between sulfur and selenium are abundantly obvious. For example, selenium is found in metal sulfide ores, where it partially replaces sulfur; both elements are photoconductors—their electrical conductivities increase by up to six orders of magnitude when exposed to light (Moss 1952).

Somewhat like the post-transition metals, the coactive nonmetals have represented terra incognita in terms of a holistic treatment. We record a dozen different organisational arrangements and class names for them, including other nonmetals. To my knowledge this is the second time the relationships among the nonmetals in this part of the periodic table have been delineated in other than a group-by-group or perfunctory manner. --- Sandbh (talk) 08:43, 30 July 2020 (UTC)[reply]

Clockwise 45° rotation

To properly gauge the diagonal relationships among the non-metals, the arrangement of the early non-metals can be rotated clockwise by 45 degrees to bring their diagonal relationships into the vertical.

O, being the shape it is, minds it own business. ^_^

The new arrangement suggests four extra diagonal relationships among the non-metals. These are found in the literature but not recognised as such:

B → P

1. B₂O₃ and P₄O₆ are each white polymeric glass-forming acidic oxides
2. Boron‐phosphorus compounds and multiple bonding

Si → Se

1. SiO₂ and SeO₂ are each white polymeric glass-forming acidic oxides
2. New developments in the chemistry of silicon selenides
3. Si and Se: Two vital trace elements that confer abiotic stress tolerance to plants
4. Si_xSe_1−x glasses with x ⩽ 0.17 exhibit remarkable systematics

C → S

1. CO₂ and SO₂ are each colourless glass-forming acidic oxides (CO₂ at 40 GPa)
2. Organosulfur compounds
3. CS₂, which polymerizes upon photolysis or under high pressure to give an insoluble material called car-sul or "Bridgman's black", named after its discoverer; trithiocarbonate (-S-C(S)-S-) linkages comprise, in part, the backbone of the polymer, which is a semiconductor
4. C₃S₂ is a deep red liquid that readily polymerizes at room temperature to form a hard black solid

H → O

1. The two together form aqua vitae.
   Amorphous ice, as used in cryogenic electron microscopy
   , is a glass.
2. Water is a spectacular anomaly. Extrapolating from the heavier hydrogen chalcogenides, water should be "a foul-smelling, poisonous, inflammable gas…condensing to a nasty liquid [at] around –100° C". Instead, due to hydrogen bonding, water is "stable, potable, odourless, benign, and…indispensable to life" (Sacks 2001, pp. 204–205). Other H-O compounds are the peroxide, trioxide, tetroxide, and pentoxide. Alkali metal ozonide salts of the unknown hydrogen ozonide (HO₃) are also known; these have the formula MO₃.
3. There are the ubiquitous ionic forms namely the hydroxyl anion OH^– and the hydroxonium H₁₃O₆⁺ cation.
4. Finally, there is the protonated superoxide HO₂ or hydroperoxyl. This plays an important role in the atmosphere and, as a reactive oxygen species, in cell biology. See: HO₂•: The forgotten radical.

• Sacks O 2001, Uncle Tungsten: Memories of a chemical boyhood, Alfred A Knopf, New York

In the regular PT these four relationships appear as putative knight's move relationships. --- Sandbh (talk) 05:16, 3 August 2020 (UTC)[reply]

Categories more broadly

I can now breathe a huge sigh of relief, as it would have really spoiled my day to have two of my best WP friends have a falling out with each other. I do have a few thoughts

1. I am a bit queasy about the idea of getting a journal article published in order to have something in a RS that we can quote. In writing this now it occurs to me that I should have AGF and presumed that this was not the only or even the primary motivation, and also assumed that there would be no attempt to self cite unless it was picked up by others. (God help us if disputogen ever appears in a RS.)
2. Submitting a dispute about the appropriateness of citations from technical articles seemed to me to be a fool's errand. The WP denizens who would be likely to respond to this would be very unlikely to have the stamina to read through all of the detailed technical material to say nothing of the technical expertise to make sense of it all. I did have some ideas about how we could have created an appropriate resolution process, but thankfully it was not needed.
3. The concern about our categorization scheme being WP:OR does raise a bit of a niggle with me. But I agree that it does serve a useful purpose pedagogically and in arousing interest and engagement, so I am loathe to throw the baby out with the bathwater. One of the dangers of the YBG rules is that if we use a scheme satisfying those rules it might tend to imply greater certainty than actually exists. It might be helpful to seek out presentation schemes that imply less certainty. We have considered and rejected using stripes or other multi colored techniques, but maybe there is some other way.
4. RL and WP stress are real problems, and if they occur together, they compound the stress. Wikibreaks or semibreaks can be very helpful, especially if used as a prophylactic before the onset of symptoms rather than as a curative afterwards. For several years now I have taken an annual wikibreak, and this has proven to be very helpful
5. I had some more points that I cannot remember now. Sigh.

All the best! YBG (talk) 07:14, 8 August 2020 (UTC)[reply]

@YBG: It's good and refreshing to hear from you.

OR. Our categorisation scheme is not OR, is it? AM, AEM, Ln, An, TM, PTM, Metalloids, NG are found in the literature. The remaining nonmetals were called by our WP:ELEMENTS predecessors as other nonmetals. We now call them reactive nonmetals which, well… they are(!), compared to the NG. This term is found in the literature: "The reactive nonmetals include the halogens and other nonmetals" (Burns & Hill 1995, Essentials of chemistry, p. 186). Our PT is a summary visual depiction of what is written in the literature.

YBG rules. Thank you for reminding us of the YBG rules. That is another great outcome of our work here. I suggest there is no meaningful danger of a YBG scheme implying greater certainty than actually exists, in the same way that this is not an in issue for the concept of a chemical group. We discuss this in our periodic table article, thus, "Placing elements into categories and subcategories based just on shared properties is imperfect. There is a large disparity of properties within each category with notable overlaps at the boundaries, as is the case with most classification schemes."

Non-metal categories. More deeply, there were the series of mega-discussions about the loathed "other nonmetals" category, which led to where we are now, with (a) reactive nonmetals and (b) NG, as the most suitable high-level unobjectionable solution. My recollection is we were stymied by the seemingly uncategorisable nature of the other metals.

Coactive nonmetals. I suggest a scheme of coactive, halogen, and NG nonmetals, meets the YBG rules. A bonus is that these three categories already appear in the literature as other nonmetals, halogen, and noble gas nonmetals. My reservation is that "coactive nonmetals" does not appear in the literature as a name for the other nonmetals. That said, "coactive" is a real word.

I intend to publish this scheme as an update to my first scheme in FoC. It'll be a good to bring more characterizational certainty to the other nonmetals, which the coactive nonmetals label does, in five different ways.

The "other" ^_^ thing is that this will be an outcome of our endeavours here. I might write it up in a journal but I'm only standing on the shoulders of WP:ELEMENTS, and other editors. We finally cracked the other nonmetals mega-conker.

The nonmetal categorisation landscape, aside from the metalloids, halogens, and NG, is schemozzle anyway, and that surely gives us the flexibility to choose which name we use for {H, C, N, O, P, S and Se} in the interests of building a better encyclopaedia. The rubbish name "other nonmetals" partly explains why Zuckerman and Nacho (1977) said "The marvelous variety and infinite subtlety of the non-metallic elements, their compounds, structures and reactions, is not sufficiently acknowledged in the current teaching of chemistry."

The importance of classification. From: Minelli, A.: The nature of classification: Relationships and kinds in the natural sciences—By John S. Wilkins and Malte C. Ebach. Systematic Biology. 63 (5), pp. 844–846:

"At any given time, during the historical development of a scientific discipline, classification of available evidence offers itself as the explanandum that asks for a theory (or alternative theories) able to explain it. But this is just one segment in a potentially unending chain of recursive relationships between classification and theory. Theory and classification indeed change over time. As a consequence, the theory that provides explanation for the data organized in a classification at a given time can influence subsequent classificatory effort, and so on. “By means of this a discipline advances: each new pattern raises questions that call for explanations, and each verified phenomenon or fact gives a new pattern” (p. 163). What counts as a fact or a theory is a matter of temporal relativity. The authors’ “concern is that we do not replace observation with theory and think that we have made some progress. Science is founded upon empirical observations, no matter how these are tied up with local and cross-disciplinary theoretical commitments or stances. Once we abandon this aspect of science…science becomes little more than a matter of worldviews and epistemic statements of faith” (p. 163)."

That's why, as I see it, it's important to strive to get the nonmetals right. Sandbh (talk) 04:48, 9 August 2020 (UTC)[reply]

@YBG, Дрейгорич, and R8R: Regarding colour schemes, here's a suggestion. Not for the choice of colours, but to instead show that only seven colours are required. Note especially, that the transition metals and noble metals have the same colour (just as they do now), but that the noble metals are intentionally flagged or "crowned" to show their noble status. I've shown other nonmetals, rather than coactive nonmetals as R8R, so far, does not think coactive nonmetals will do. Sandbh (talk) 01:51, 12 August 2020 (UTC)[reply]

Is it necessary to separate the halogens from the other nonmetals if we're not separating the alkali and alkaline earths from each other? I would propose six categories: active metals (groups 1+2), transition metals (d+f blocks), post-transition metals, metalloids, reactive nonmetals (non-noble gases... pre-noble gases?), and noble gases. ― Дрейгорич / Dreigorich Talk 03:32, 12 August 2020 (UTC)[reply]

@Дрейгорич: The alkali metals and the alkaline earth metals are reasonably comparable. In contrast, the traditional aspect of teaching the periodic table is to contrast the alkali metals with the halogens (although I see YBG has some thoughts about this which I haven't yet looked closely at). So that'd be a relatively strong consideration. I've never seen it but I'd expect dropping some sodium into bromine would be illustrative, if not explosive. Another observation is the distinction between the halogen nonmetals and the other nonmetals is relatively easily made. So:

Have a look at Table 1, and see how the halogens have consistently high IE, EA and EN.

Similarly there here is a pretty good distinction between the transition metals and the Ln/An. Sandbh (talk) 05:35, 12 August 2020 (UTC)[reply]

Only EA seems to be a good distinguisher between the halogens and the other reactive nonmetals, as the other criteria mix the reactive nonmetals with the halogens - there are reactive nonmetals that score higher than halogens. Only EA makes a clear division between them. ― Дрейгорич / Dreigorich Talk 12:18, 12 August 2020 (UTC)[reply]

@Дрейгорич: What distinguishes the halogens is that they’re the only nonmetals each having high values for IE and EA and EN. The noble gases are distinguished by, among other things, not having any EA. Before the noble gases were discovered, nitrogen was called a noble gas. Sandbh (talk) 13:39, 12 August 2020 (UTC)[reply]

Interesting. Didn't know that, thanks. ― Дрейгорич / Dreigorich Talk 16:05, 12 August 2020 (UTC)[reply]

Unification of AM and AEM

I think that a unification of AM and AEM into one category is rather uncalled for, for Wikipedia at least. Both names are better known than any combination of the two.

I would assume that a unified s-block category also calls for more unification: one category for the f-block, for instance, and fewer categories for the p-block. Yet we still have two categories for the d-block and five for the p-block (but also zero for the f-block). I don't see a good consistency here.--R8R (talk) 11:44, 1 September 2020 (UTC)[reply]

@R8R and YBG: The AM and AEM names are better known, I agree. That said, our table is not a group-by-group table. Rather, it is more of a metallicity-nonmetallicity table, consistent with the seven quotes from the literature in the above quote box. That is why we do not have categories for the individual p-block groups, apart from the noble gases. From that perspective, the categories of AM and AEM are somewhat inconsistent. A unified s-block category does not necessarily call for more unification; chemistry is full of idiosyncrasies.

In any event, as well as our metallicity categories, we also show the group names in the bigger table, and we used to show the Ln and An labels too. Sandbh (talk) 08:11, 5 September 2020 (UTC)[reply]

I'm not sure our table is a metallicity-nonmetallicity table, I wouldn't put it with that. Only our p-block really has this theme. The d-block, for instance, is collectively called the "transition metals" even though they differ a lot by chemical properties (compare, say, copper and zinc on one hand and gold on the other). The existence of a lathanide category is not covered by the description of our table as a metalicity-nonmetalicity table, and the actinides are rather diverse, too, perhaps too diverse for a single grouping if we consider that it's best to split off the four main halogens from the rest of the reactive nonmetals. However, we use those names (TM, Ln, An) because they are widely known (unlike the name "reactive nonmetals" which we can sacrifice because it's not that well-known), and that's the best criterion for Wikipedia I can think of, and that's why we use them. The same goes for AM and AEM. We should stick to these categories here to remain oriented towards the general reader and the description they may find elsewhere. This doesn't invalidate the idea as a whole, I'm merely saying that this is not the place.--R8R (talk) 10:20, 5 September 2020 (UTC)[reply]

@R8R and YBG: As per the literature, the transition metals represent a transition from the physically weak but chemically strong metals to their left, and the physically and chemically weak metals to their right. A quick look at the electronegativity values for the s-block metals and the f-block shows a similar gradation in diminishing metallic character.

The complete L-R gradation is s > f (i.e. Ln/An) > d (transition) > p metals > metalloids > pre-halogen nonmetals > halogen nonmetals ~> noble gases. This phenomenon is discussed in our periodic table article.

AE and AEM are not worth keeping as category names as we include them along the top of our main periodic table as group names, together with all the other group names including the halogens. That is the beauty of it: being able to appreciate the table by category and by group. Having the AE and AEM as categories and as groups is an unnecessary duplication. Sandbh (talk) 13:16, 6 September 2020 (UTC)[reply]

I agree with @R8R: in his doubts that our table is a metallicity-nonmetallicity table. Our color scheme is certainly oriented in that direction, and I suppose that one could say that the color scheme is one of the distinguishing features of the enwiki PT. I take issue with @Sandbh:'s previous statement our periodic table is not a groupic table. It is a metallicity table. I think his recent statement That is the beauty of [the enwiki PT]: being able to appreciate the table by category and by group.

I agree with @Sandbh: that having the AE and AEM as categories as well as groups is an unnecessary duplication. On this same basis I say that having the Halogens as both a group and as a category is an unnecessary duplication. Of course, the same logic applies to the noble gasses - but as I've said before, if any group is distinct enough to merit being both a group and a category, it is the noble gasses.

—YBG (talk) 23:08, 6 September 2020 (UTC)[reply]

@R8R and YBG: I suspect our table is not the first to use colour categories and that, these days, names like alkali metals, and alkaline earth metals sound rather old fashioned, although still part of the lexicon. Halogens and noble gases are fine. We wouldn't really have a category and a group each called "halogens". There would be the group 17 halogens (F, Cl, Br, I, At, Ts); and the halogen nonmetal category (F, Br, Cl, I):

--- Sandbh (talk) 03:57, 7 September 2020 (UTC)[reply]

Here are several examples from the literature, including the use of the pre-transition metal label:

1. "The pre-transition metals. These occur in Group IA and IIA of the Periodic Table, and for a number of purposes it also convenient to include with these the Group III metals, Al, Sc and Y…" Phillips and Williams (1966, p. 4)
2. "In contrast , the coordination chemistry of the ocean would , at first, seem to be the exclusive province of the pretransition metals; this is seen clearly by looking at an average composition of an ocean" (ACS 1967, p. 256)
3. "The ionic hydrides chiefly comprise the pre-transition metals: alkalis, alkaline earths, etc." (Goldschmidt 1967, p. 446)
4. "The chemistry of these elements [AEM] resembles that of the IA metals to a large degree. (Hamm 1969, p. 369)"
5. "It is convenient to deal with the subject by considering the derivatives in turn of the three main types of metal: (a) light and pre-transition metals (Li, Mg, Al etc.); (b) the post-transition metals (Zn, Sn, Pb etc.); (c) the transition metals (Ni, Pd etc…" (Nyholm 1970, p. 35)
6. "The difference between the Group I and Group II elements (except Be) is more of degree than kind." (Choppin and Russell 1972, p. 334)
7. "This concept will be considered in Chapter 2, but suffice it to say here that complexes of the pre-transition metals (Na+, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Al³⁺) are held together by electrostatic forces…" (Eichorn 1973, p. 4)
8. "In this scheme, the alkaline-earth metals, Ca, Sr, and Ba, may be regarded as pre-transition metals and the noble metals, Cu, Ag, and Au, as post-transition metals." (Collings 1984, p. 46)
9. "Aluminium and the elements of groups 1 and 2 are classed as pre-transition metals…" (Cox 2012, p. 188). Cox also discusses the properties of the pre-transition metals as a whole, as did Deming (1940, pp. 650‒672), the guy who popularized the medium-long form of the periodic table (except he called them light metals).
10. "Pre-transition-metal oxides (e.g. MgO, Al₂O₃, etc.) usually are good insulators and inert to redox gas molecules" (Wang & Gouma 2012, p. 169).
11. "Alkali (Group IA) and alkaline earth metals (Group IIA) share a host of common physicochemical attributes." (Arevalo 2016) [1]

--- Sandbh (talk) 06:41, 11 October 2020 (UTC)[reply]

@Sandbh and YBG: I don't see how "alkali metals" or "alkaline earth metals" are old-fashioned. Is it a personal feeling? If not, are "halogens" and "noble gases" also not outdated? If not, why those two aren't outdated while the other two are?

I don't see why having a column and a category overlap completely is that much of a problem. I really don't. And if that confusion weren't enough, we also have the "noble gases" category that's not going away, which is precisely a group-category. Why is it okay in that case but not in the other?

I'm not saying that the idea is unworkable, not even in principle. I'm noting that, however, we in Wikipedia are a tertiary source, and we must first of all reflect on what others say. While I don't doubt that the 'pre-transition metal" label exists, AM and AEM are both well-established categories, both more widely known than the merger, as you noted yourself a few messages ago. That is the ultimate argument as I see it. That was also how we ended up with a -La-Ac group 3: not because it's better but first and foremost because it's more common, and that's a fine line of argumentation as I see it, and that's the number one line of argumentation as long as Wikipedia is concerned. This change is uncalled for here at the time; this assessment may change if chemical literature embraces the "pre-transition metal" label more closely. It may be a worthy change but it shouldn't start here.--reaR8R (talk) 17:28, 9 September 2020 (UTC)[reply]

@R8R: For the record, I think that the old fashioned argument should be completely disregarded.

To me, the crux of the matter is why we have categories at all. I suggest that the reason why we have categories is to provide some broad, high-level organization that enables the reader to see the structure of the PT. A few general principles flow out of our primary goal, serving the reader.

1. The number of categories should be small, ideally
   7±2
   .
2. The categories should present information that is not otherwise obvious in the PT.

Our current 10 categories (counting unknown properties) seem to me to be unwieldy, particularly in how they make exacerbate the difficulties of selecting a good set of colors that satisfy the need for contrast and accessibility issues. (This is the reason why I apply the

7±2

ideal to the entire set of categories and not separately to the metal and nonmetal categories, which would be sufficient for "chunking".) Consequently, I am inclined to oppose Sandbh's proposal to subdivide the reactive nonmetals into pre-halogens and halogens, and I am generally inclined to support Sandbh's proposal to merge AM and AEM.

I say "inclined" because this reason in and of itself is not sufficient for a final decision.

Let me start by making the case for the noble gasses being a one-group category. The NG are so different from all of the other elements that a perfectly reasonable 2-category PT would have the NG in one category and everything else in another category. All of the other elements share a common characteristic (reactiveness) that none of the noble gasses have. Yes, it is true that the NG form compounds, but only under coercion. And it is true that the gold group is also noble. But the gap between the least most-reactive noble gas and the least-reactive of the other elements is a wide gulf indeed. Thus it makes good sense for the NG group to be elevated to category status.

Now consider applying the same standard to groups 1 and 2.

Yes it is true that the AM elements share common characteristics that none of the other elements share. Likewise, the AEM share common characteristics that non of the other elements share. But the pertinent questions are much stronger. Do all of the non-AM-elements share a common characteristic that the AM lack? Does that characteristic divide the AM and non-AM with a wide gap? Do all of the non-AEM-elements share a common characteristic that the AEM lack? Does that characteristic divide the AEM and non-AEM with a wide gap? If these are the true, then I would heartily agree that the AM group and the AEM group should reasonably have elevated category status.

But this is not the case, and in fact the AM and AEM, while different, share many common characteristics.

By representing groups/families as labeled columns, our PT already identifies the AM and AEM. If there were only 4 or 5 other categories, I would be in favor of keeping the AM and AEM separate. But because we have 7 or 8 other categories, I believe our categorization scheme will be improved by merging them into an "active metal" or "pre-transition metal" category. The terms "alkali metal" and "alkaline earth metal" will continue to exist as group/family names, just not as separately named and separately colored categories.

YBG (talk) 18:52, 9 September 2020 (UTC)[reply]

I appreciate the YBG reasoning here, as in: keep it as a category if it can stand up to all other elements. It's a strong test. However, when arguing that 10 categories is unwieldy, particularly in how they make exacerbate the difficulties of selecting a good set of colors that satisfy the need for contrast and accessibility issues. I've made some off-wiki research and excercises and one can be sure, even 'only' seven categories do not eliminate accessability-issues (like colorblindness, contrast). Also, those issues could be alleviated by other methods. All in all, I appreciate the tough requirements, checks and tests YBG introduces; and I'd prefer this discussion not be coerced because of sole coloring issues. IOW: if the PT would need 14 categories, coloring is the smallest problem. -DePiep (talk) 19:15, 9 September 2020 (UTC)[reply]

• I'm here, weeks later, for the topic of Unification of AM and AEM. (Other issues are discussed in this thread too - trying to keep separation).

1. I am impressed by the R8R logic expressed: the names are strong and well-established, so unification is not an improvement (my words here, it is more complete in the R8R posts).

2. I'd expect a wide and thorough description here about how similar these AE and AEM elements chemically are. That would be the first and foremost reason to merge (whatever naming problem would arise). Isn't there an earlier thread in the archives? Nothing from

WP:CHEMISTRY

?

For both reasons I currently support to keep the distinct AE and AEM categories. -DePiep (talk) 20:05, 27 September 2020 (UTC)[reply]

@

WP:IAR application. We can maybe look at that and see how much better exposition for IAR counts over smaller representation in the literature. That's what we did deciding which elements are metalloids, that's also more or less what we did and can be done on the "are group 12 elements transition metals" question, that's to some extent what was done on group 3. But when the literature is very clear as expressed by 1, I don't think we need to or even should go down to 2 here for Wikipedia. Double sharp (talk) 23:31, 27 September 2020 (UTC)[reply

]

Of course, Double sharp, a unification should follow from literature not from OR here. And that is what I meant to say: there sure is enough literature that describes their common (categorical) properties. However, in this thread it is treated as a pre-existing certainty (but the adjusted/created article would need such sources right?).

Anyway, here is a similar discussion from March 2013.

To consider: I propose new category name to be "Alkaline and Alkaline Earth Metals", thereby following R8R's preference to maintain those well-established names. Name length should not be an issue. -DePiep (talk) 08:11, 29 September 2020 (UTC)[reply]

The nature of aluminium

Across the group 1–16 metals (excl. the Ln/An) and metalloids I looked at normalised values for IE; EA; EN; standard reduction potential; MP; packing efficiency; and BP. Effectively, no matter how I weight these chemical and physical values, aluminium always falls between magnesium and beryllium. This lends strong support for it being categorised with the AM, and AEM, per Deming, and Cox, rather than with the PTM.

The overall sequence then looks like this

I'll post some data in due course, hopefully including the Ln and An. Sandbh (talk) 05:14, 17 October 2020 (UTC)[reply]

About halogens

@

@

AEM

as displayed group names, noting your support for bifurcating the reactive nonmetals?

@YGB: May I ask for a little movement on your part in supporting a reactive nonmetal split, noting the WP PT has featured such a split for the last 16 of 18 years (with ten[!] categories, not counting the unknown properties pseudo-category), and that I support your proposal for a group 1-2 merge?

@DePiep: thank you for chiming-in with your thoughts.

For my part I will support the retention of metalloids as a major category, noting they are no more than chemically-weak nonmetals, a fact that has been known, and recorded in the literature for over 120 years.

I feel neither of my requests represent die-in-a-ditch matters. Sandbh (talk) 06:44, 10 September 2020 (UTC)[reply]

re the halogen group or category name by Sandbh. For sure, halogen is undisputed a group name. That should do, it is in our PT. A more relevant question would be whether we are fine with the words "metal, nonmetal" being only present in secondary order (to be deducted from the legend). Now, I do not see why squeezing 'halogen' into a category name too would help or clarify anything. (Even the construction cat:halogen nonmetals / grp:halogens is not helpful except for using the word once more; consider "f-block lanthanides"). Then re lamenting "—to my complete astonishment—we got rid of it": well, who wrote "...astatine is currently better classified as a metalloid" then back in 2012, and more? I don't think this meandering and free thought releasing helps towards a sound decision base for category changement. Is there a basic structure of approach here I am missing? -DePiep (talk) 14:36, 10 September 2020 (UTC)[reply]

@DePiep, R8R, and YBG: For clarity, here is what I have in mind:

The labels metal and nonmetal are included in group or category names where appropriate.

We took a considered approach to categorising astatine. Immediately following its production in 1940, early investigators considered it a metal. In 1949 it was called the most noble (difficult to reduce) nonmetal as well as being a relatively noble (difficult to oxidize) metal. In 1950 astatine was described as a halogen and (therefore) a nonmetal. In 2013, on the basis of relativistic modelling, astatine was predicted to be a monatomic metal, with a face-centred cubic crystalline structure.

We first changed it from a nonmetal to a metalloid. In 2013 it was predicted to be metal. We didn't doing anything about that for a while. Since the article was published it has been cited 35 times without dissent. So we changed the category of At to a post-transition metal.

The above colour category proposal means there is still, as there always has been, a halogen Group 17, comprising the nonmetals F, Cl, Br and I, and the metal At.

If no one likes highlighting the noble metals then that is another matter I won't die in a ditch over.

As I see it, the structured approach to categories is:

1. good classification science;*
2. categories are usually defined by more than two attributes;
3. such attributes are found in the literature;
4. categories may change over time as new insights are uncovered
5. the 7±2 rule where feasible;
6. categories should be beneficial to an economy of description, to structuring knowledge, and to our understanding; and
7. hard cases should constitute a small minority.

* i.e. distinctive categories, whilst acknowledging there is a spectrum of attributes within each class; that the distinction between classes is not absolute; and that boundary overlaps will occur as outlying members in each class show or begin to show less-distinct, hybrid-like, or atypical properties

The context is:

1. for the past 16 out of 18 years we have had three nonmetal categories, with good reason;
2. "other nonmetals" is a less than desirable category name; and
3. the difference between the AM and AEM is more of degree than kind.

--- Sandbh (talk) 01:33, 11 September 2020 (UTC)[reply]

I've got a few thing to say about this.

Could I please move?

I could in principle. For instance, if we were writing a book, I think we could have a discussion about whether such a move is a good thing; if it's not clear, then to what extent it is and to what extent it is not, and from there we could have decide whether it was worth it. I don't intend to insist on anything I like best if other things are good enough and somebody feels strongly about them.

House rules

That would be if we were writing a book and thus were free with respect to what we wanted to write. However, we are not writing a book. We are writing for an encyclopedia, which has its own house rules. The principal rule I keep referring to is that Wikipedia is a tertiary source and thus we are supposed to first and foremost what other sources say. This is very important: when in Rome, do as the Romans do.

Are alkali metals and alkaline earth really all that similar?

I'd say whether the difference is of degree or kind is secondary to whether the combined category could exist in this encyclopedia given its house rules.

Other nonmetal?

My thinking was and is that "other nonmetal" is not a term worth replicating as it is generic and meaningless. This is a unique situation, or if I'm wrong and we once upon a time also had "other metals," then I'm sure I propagated a move to "post-transition metals" to add some meaning to the category.

What do the sources say?

According to Google Ngram, the term "pre-transition metal" was in 2019 roughly 1,000 times less popular than "alkaline earth metal" and roughly 4,000 times than alkali metal. Interestingly, the idea that "halogen" and "noble gas" are most popular names for a chemical category of elements is contradicted by the graph, which shows that "alkali metal" was consistently more common than the latter.
This graph also shows the comparison between "metalloid" and "chalcogen" and "pnictogen." It can be seen that "metalloid" is more popular than both, however, it is still less popular than "halogen." The category of metalloids, however, owes its appearance to the existence of the general terms "metal" and "nonmetal". The term "metal" is very well-known in chemistry and beyond, and if you were to add it to the graph, it would dwarf all the other lines, including that of the halogens ("metal" was roughly 75 times as popular as "halogen" in 2019).

There are still groups, we could use those two names there

With all due respect, I don't think this is anything that resembles a trade-off. I never thought about groups in our big table. What I have always looked at is the small table in the infobox, and I sometimes think about the table at the bottom of our articles. This was also never the reason why I advocated the removal of the halogens category back in the day, so I don't see why it could matter now.

In conclusion

If there were a category even remotely resembling in popularity AM and AEM, we could consider it. But there isn't one, so there is nothing to change to given the house rules of Wikipedia. The thinking could be different on a different platform but here, it stands.--R8R (talk) 11:43, 11 September 2020 (UTC)[reply]

Ngrams, House rules

@R8R, YBG, and DePiep: In an ngram search, the singular forms AM, AEM and halogen are less than relevant since the subject matter is categories of the element types, not individual examples of the elements concerned.

A search of the plural forms yields the ratios you can see in the table. Bold = IUPAC-endorsed. [G] = Group name.

From these results, the recipe for colour category names features, or has featured, a combination of [1] literature popularity; [2] pragmatism; and [3] convenience. Thus, we:

• use transition metals in preference to the IUAPC-endorsed transition elements, as the latter is less popular;
• use metalloids since this category name is more popular than some other IUPAC names, including AEMs (which we do use);
• use post-transition metals as the best of a bad choice;
• used polyatomic nonmetals and diatomic nonmetals as a convenient way to reflect the most popular practice in the literature of having there being two categories of "reactive" nonmetals.

Our colour categories appear to be arbitrary in at least three aspects:

1. no mention of rare-earth metals, a popular and IUAPC-endorsed name;
2. no mention of noble metals, a popular and IUPAC-endorsed name; and
3. the absence of two categories for the "reactive" nonmetals, contrary to the literature.

Item 1 is trumped by the popularity of the lanthanide category.

Item 2 should be addressed, in accordance with our house rules, and this can be done easily, as suggested.

Item 3 should be addressed in accordance with our house rules, and this can likewise be done easily via judicious use of the "halogen" noun, as pre-halogen nonmetals (in the absence of anything better c.f. post-transition metals, as mentioned courtesy of R8R) and halogen nonmetals, which is precisely what they are.

Is there a case for merging the AMs and AEMs consistent with our house rules?

1. We have a precedent i.e. the removal of the highly popular halogens category.
2. The literature provides a precedent: we are not breaking new ground.
3. The alkaline earth metals category is no more popular than the rare earth metals category, and we do not show the latter (for a good reason).
4. While AMs and AEMs warrant separate articles, they are not worth separate colour categories given the difference is one of degree rather than kind. Further, the progenitor of the AEMs, beryllium, is not alkaline; the second member of the AEMs, magnesium, is not an "earth": that is why there is a need for an article on the AEMs, to explain what is going on. Historically, only calcium, strontium and barium were regarded as alkaline earths.
5. The frequency of the s-block metals category name (3½) is remotely—per R8R's request—as popular as the average (77½) of the AMs and AEMs.
6. s-block metals is x3 as popular as the post-transition metals and reactive metals, which we do show.
7. s block is as popular as the AEMs; metals is 250x AEMs.
8. Light metals (15), per Deming, is not unreasonable, being even less remote from the AMs and AEMs.
9. We have a limited amount of real estate available on our small colour category periodic table; an internally weak category is one category too many, consistent with the YBG rules i.e. #3, insufficient between-group dissimilarity. Even the name AEMs was derived from the fact that that the hydroxides of calcium, strontium, and barium, like sodium and potassium hydroxides, have alkaline properties. Said another way, the s-block is not worth a split, whereas the other blocks are (1 split for the f-block; 2 for the d-block (3 if you include the noble metals); and 4 "splits" for the p-block, where the metals meet the nonmetals.
10. Aspirationally, in terms of legibility and readability, this is closer to the worthy 7±2 rule. On an associated note, the "too loud" red shade of the AMs is removed.
11. The above items are consistent with building a better encyclopaedia; there is no OR.
12. The above items are not subject to the deliberations of an IUPAC project. Further we do not follow IUAPC recommendations with respect to the transition metals category name, nor does IUPAC recognise post-transition metals; metalloids (it has a historical record of disavowing its use, or preferring semimetals), or reactive nonmetals.

--- Sandbh (talk) 07:20, 13 September 2020 (UTC)[reply]

This is going to be a partial reply to the 12 items. Perhaps it may need added to in the future.

My thinking is that we as a tertiary source (I say this phrase a lot because it really is important) should use categories that are well-known and are well-defined in the literature. The list of such names goes more or less like this: metal, metalloid, nonmetal; alkali metal, alkaline earth metal, rare earth metal, lanthanide, actinide, transition metal, platinum group metals, pnictogen, chalcogen, halogen, noble gas. There are some other names that I would advise against on basis of their ambiguity: for instance, I have no doubts about what the composition of the alkali metals group is; what is the composition of the group of noble metals, does it include, say, gold? mercury? On top of that, we have one more constraint, which is that categories should not overlap. This set of constraints gives us two problems: one is that some categories do overlap and we must choose (we even have an unsolvable overlap between transition metals and lanthanides and actinides), which is why we don't use some names, for instance, rare earth metals and platinum group metals. On the other hand, there are elements that didn't fall in any category, such as carbon, and as such we had "other metals" and "other nonmetals." We eventually changed "other metals" to more descriptive names, IIRC "poor metals" and then "post-transition metals". "Other nonmetals" was harder to get rid of.

Removal of "halogens" is not a precedent. It really isn't, I'm not stretching anything to fit my liking. There were a few advantages other than editorial preference: intersection of halogens and metalloids and existence of a meaningless name (other nonmetals). Neither is a concern with the proposed move in s-block, where we would merely remove two well-known names in exchange for a less-known one to match some editorial preference.

"s-block metals" is 40 times less popular than "alkaline earth metals" and 115 times than "alkali metals." I think that's a bit too distant. Notwithstanding that, I would argue that "s-block metals" is not a name at all, it's merely a description. A name adds some image to a group; even the transition metals are about some transition. Compare "alkali metal" (a name) and "group 1 metal" (not a name). Names are more reader-friendly, and as such I propose we use them as we always have.

Can you specify where IUPAC endorses "noble metals"? The Red Book doesn't mention this name: "The following collective names for like elements are IUPAC-approved: alkali metals (Li, Na, K, Rb, Cs, Fr), alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra), pnictogens8 (N, P, As, Sb, Bi), chalcogens (O, S, Se, Te, Po), halogens (F, Cl, Br, I, At), noble gases (He, Ne, Ar, Kr, Xe, Rn), lanthanoids (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), rare earth metals (Sc, Y and the lanthanoids) and actinoids (Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr)." (Red Book, 2005) The Red Book also mentions "transition elements" and "inner transition elements."

I will leave aside the discussion whether the s-block merits a split because it's up for sources, not us, to introduce a new name since there are already some names, but such a name is yet to be seen. Just as I won't ask whether Be or Mg should really be in the same category as Cs.

The red of alkali metals is easy to fix. I'd say it's a few hours' work to improve the existing colors. As DePiep (rightly) notes, color choice should not be a consideration for category choice.

We don't need a precedent for a change; we need to see that the number of instances is at least comparable. That is not the case. Removing two well-known names for an unknown or worse, dubious name (I'd argue aluminum is a "light metal," for instance) is not helpful in our quest for building a better encyclopedia. I once again note that I am primarily concerned with encyclopedia-building, rather than pure categorization where more freedom is allowed. It could very well be that a common category for the s-block metals could help you write a better book of your own; I'm merely arguing against using that category in our encyclopedia for the time being. If a name ever picks up, we can reconsider.--R8R (talk) 15:03, 19 September 2020 (UTC)[reply]

• • I have taken my time to consider what you said and formulate my response based on this close consideration. I'll try to write it down soon enough.--R8R (talk) 10:57, 14 September 2020 (UTC)[reply]
  • So will I. -DePiep (talk) 22:17, 15 September 2020 (UTC)[reply]

For starters: Sandbh how is popularity an agument at all? -DePiep (talk) 23:07, 15 September 2020 (UTC)[reply]

DePiep: As an encyclopedia we aspire to take account of the literature. The Google ngram bookworm has been criticised for an overabundance of scientific literature! That's the kind of criticism I like. Sandbh (talk) 00:31, 16 September 2020 (UTC)[reply]

(point-of-return for DePiep) -DePiep (talk) 23:13, 18 September 2020 (UTC)[reply]

Sandbh responds to R8R

@R8R, YBG, and DePiep: Responding to R8R.

Tertiary sources. Yes, I agree these are important. So are well-known, well-defined categories.

Yes, I agree these important aspects sometimes clash, or cannot be so well-attained.

For example:

• At the very start, the boundary between metals and nonmetals is blurry.
• Halogen is a well known collective term, and the most popular of the IUPAC-endorsed names. We do not show it since it clashes with the metalloid category.
• The metalloid category is not well defined. Some authors do not recognise such a category. However, we can at least see, based on the COSMIC database (z = 194), which elements are most commonly recognised as metalloids.

Already we have to exercise some editorial pragmatism. This does not matter as long as we provide the context for doing so, and the basis for the decision.

Noble metals. Rayner-Canham (2018) recently considered how to parse the transition metals, on chemistry grounds. He surveyed the TM classification literature. His biggest sub-category was the noble metals, as PGM + gold. Silver, in comparison, is so much more chemically reactive and has such a different chemistry. Mercury is effectively not a transition metal. Once again we need to exercise some editorial pragmatism. IUPAC does not endorse noble metals as category. Nor do they endorse post-transition metals; metalloids; and reactive nonmetals. The great German text by Wiberg comments, "In place of the noble gases, the transition metal grouping has the noble metals." (2001, p. 1133).

Categories should not overlap. It’s a commendable aspiration but very many categories overlap. The overlaps are not so important. More important is that the categories provide an economy of description, a tool for structuring knowledge, and can also lead to deeper understanding.

Overlaps are solvable. We can show them using diagonal lines of demarcation, as some other authors do. The German Wikipedia has a nice table, in its lead, featuring some of these. This table has its own issues but we can do better.

Taxonomy of our scheme. Our category scheme is based primarily on metallicity and secondly on categories (not Groups):

I. Metals-metalloids-nonmetals

II. Categories.

Note the absence of a Roman-numeral-level for Groups. So the coinage metals, volatile metals, chalcogens, and pnictogens are not shown. Of course, the noble gases are shown as a category and that is fine. The noble gases are not a “Group” per se since they will not be able to accomodate oganesson, which is expected to be a solid, reactive (i.e. not noble) semiconductor (band gap 1.5 eV) having a sub-metallic appearance.

Census of periodic tables in chemistry (COPTIC database)
I looked up the taxonomical structure of periodic tables found in 62 more recent chemistry textbooks:

^ Groups 1 and 2

Observations and conclusions

1. The frequency with which the Ln and An are flagged is astonishing.
2. The frequency with which Groups are not flagged is remarkable.
3. 67.5% of sources include the words lanthanides and actinides on their table.
4. Given only 10% of sources (on average) flag Groups, the field is wide open after the allocation of the categories: s-block or equivalent (~20%)§; Ln; An; TM; Metalloid; and Noble gas.
5. Post-transition metals appears to be a reasonable choice for the leftover metals between the TM and the metalloids, given the limited range of names for the metals in this part of the periodic table.
6. I'm not sure I ever understood what was "wrong" about poor metals.
7. Looking subsequently at the ngram results, "Halogen" warrants a place in some fashion, as does "Noble metal".
8. The periodic table in the lead of our periodic table article is deficient given there is no immediately accompanying colour category legend (cf the German example).

§ = s-block (15%) + Active metal; Light metal; Reactive metal (~5%) = ~20%

Nonmetal categories

"While I am eager to be proven wrong, I continue to think that there is no good divide at all. I see myself agreeing on a divide with two clear self-descriptive relevant terms, but throughout all of this time, we haven't found a single one. --R8R (talk) 17:36, 10 September 2017 (UTC)

In light of item 7 above, and table 1 below, this does indeed happen.

The numerous properties that distinguish the halogen nonmetals from the remaining "reactive nonmetals" are set out in the literature. Here they are again:

† A small clarification about oxygen. Metal oxides are usually ionic. On the other hand, high valence oxides of metals, and the oxides of metalloids and nonmetals, are usually either polymeric or covalent.

‡ Since H₃⁺ is featured in interstellar chemistry this could be said to be unconvincing. Yet that is not the point. Instead, there is a spectrum of applicable properties in each category. Carbon is the most prolific catenator. Hydrogen happens to the poor cousin, that is all.

In light of these further considerations I argue that hydrogen has a not insignificant linking capacity.

Light metals

"If there were a category even remotely resembling in popularity AM and AEM, we could consider it. " R8R (talk) 11:43, 11 September 2020 (UTC)[reply]

Deming included Al among the light metals, along with the group 1 and 2 metals. It’s a good category name since that is exactly what these metals are. The link between Be and Al is strong. And light metals avoids the problems with the "alkaline earth metals" name i.e. that Be and Mg are not alkaline earths. Light metals got an Ngram of 13-15; the AM and AEMs average 77. I’d say 18% is more than good enough to regarded as, at least, "remote".

Light metals is fourteen times as popular as post-transition metals and reactive nonmetals, both of which we show.

Objective

Here's where this is headed; I've discussed replacing the lanthanides with the rare earth metals elsewhere:

A Including aluminium

ρ Transition (rare earth) metal: Sc, Y, La

✣ Transition (noble) metal: Ru-Pd, Os-Pt, Au

Rare earth metal is there in light of its ngram popularity, and the fact that at least the label "Lanthanide series" ought to be shown on our table. That is, the lanthanide category name will be retained. R8R: I see you responded to the rare earth proposal separately; I'll follow on with a response.

YBG supports a merge of AM and AEM, as do I. R8R has expressed support for two nonmetal categories, in addition to the noble gases. I support this one too.

R8R: In terms of encyclopedia-building, all of the above more closely follows the literature than is the case now. It therefore represents an improved taxonomy.

I'll draft a better PT for the lead of our article, for you all to consider.

DePiep: Grateful for your thoughts. Sandbh (talk) 06:42, 21 September 2020 (UTC)[reply]

Well-known, well-defined categories. I absolutely agree on that they are important. We are on the same foot about this.

We have to exercise some pragmatism, that's right, too. However, we must not exercise more pragmatism than we absolutely have to. This limitation is specific to Wikipedia and it's a big part of why I keep repeating it's important that we are writing a tertiary source. If halogens were more important than metalloids, then it would only be natural we had chalcogens, too, and perhaps pnictogens. Where carbon goes then remains a mystery. So in terms of a whole picture having metalloids over halogens is very clear. This groups 1-2 issue, however, does not have such far-reaching consequences; it doesn't affect anything else (I'll take it Al is fine either way).

Noble metals To quote you, "once again we need to exercise some editorial pragmatism," and therein lies the problem. This is not some pragmatism that we absolutely have to exercise. It's a good hint that we may not need this category at all. Alone, it does not prove anything, of course, because there are some ties such as whether group 12 elements should be colored as TMs or PTMs, but it's a very good sign. Yet I still don't see the need to include this term in our general classification in the first place. For example, this suggestion moves us further from the 7±2 argument that has just been used in a different circumstance. Whereas I don't think 7±2 argument is the sole arbiter, I agree with the general point that there shouldn't be more categories that there have to be. We already have those elements covered as TMs. There's no real need for more; that's just enough. Just because a term exists doesn't mean we should display it in our general classification, just as we don't display the term "chalcogen," for instance.

Categories should not overlap Once again, a quote: "More important is that the categories provide an economy of description, a tool for structuring knowledge, and can also lead to deeper understanding." The big question is, what description do we want to use. What knowledge should we structure? Could it be we wanted to display and structure too much knowledge for a single graph? I think that's a case of what we're having here. I don't disagree with what you said, I simply mean to say that it wasn't an argument for your side (or mine): you could interpret those words however you like. Having to have no overlaps, however, is a tangible limitation.

Both Johansson et al. and de.wiki use overlaps between different categories. It is well established in de.wiki that there is a halogen category and a metalloid category, most elements in these groups are not defined as anything other than halogens and metalloids, respectively. We have decided we should handle those cases by putting all elements into one group or another. Having to have a group that entirely falls into another group is something neither Johansson et al. nor de.wiki do. Perhaps somebody does, but it doesn't matter: if someone uses this kind of overlap, it doesn't mean we should. It would be beneficiary if we had established the importance of having to have an element in two groups. As I said, no such case has been shown and I don't believe there is. I regard all subcategories as not needed. If we do want to show this knowledge, we can very well do that in our articles, not in a first-level classification.

I am not convinced by the arguments in favor of the new nonmetal division per se, but I will not at this moment argue against them, mostly because I am myself not sure whether a division of reactive nonmetals could be an overall positive thing or not. The strongest argument in my head in favor of this division is that it brings back the term "halogen" into the fold, however, I'm afraid that people will assume that "halogen nonmetal" is tautology even while noting that At is not a part of the scheme. I know that, strictly speaking, there is no problem of definition, but I am afraid this name will be misunderstood and cause more confusion than there should be. I have not made my mind about that yet.

I think the term "light metal" merits a consideration based on its popularity. No question about that.

What is a light metal, precisely? If you asked me, I'd say, "it's a metal with a density of less than 5 g/cm³." That's the definition I think of when I think about this term. The problem with it is that it's not a good definition to classify chemical elements: it is about physical properties, not chemical ones. All other category names are based on chemical properties of those elements that constitute those groups. It hadn't even crossed my mind we could be considering a not-chemistry-based category names. Second, what elements would constitute that group? I think of titanium as of a light metal, and the proposed category name does not match my expectations when it comes to its constitution. That would leave me puzzled. The existing category names cause no confusion whatsoever. It is clear to me that after a consideration, having "alkali metals" and "alkaline earth metals" is a better option. I suggest we do that.

"R8R has expressed support for two nonmetal categories" -- I want to be clear about what I said, I have expressed conditional support, and the condition is that we have two good category names to use. I am still pondering whether the condition has been met. I can't say off the top of my head that it has not, but I can't say it has, either.--R8R (talk) 09:47, 26 September 2020 (UTC)[reply]

@Sandbh: I apologize for taking so long to reply. It takes me quite some time to write such long responses down and I can't always find it on working days. It is likely I may have a problem doing that in the future, too, though I'll try to respond more quickly.--R8R (talk) 09:54, 26 September 2020 (UTC)[reply]

YBG comments (1)

@R8R, YBG, DePiep, and Sandbh:

A few quick comments after a quick read-through of Sandbh's latest post.

• We do not show [Halogen] since ...

  On the contrary, we do show halogen as a group, just not as a category.

• IUPAC does not endorse noble metals as category.

  As I understand it, all IUPAC does is endorse named lists of elements. "Category" is term with a specific meaning at enwiki and it would be best not to confused things by using it in other ways or in ambiguous ways.

• The frequency with which Groups are not flagged is remarkable.

  I'm not entirely sure what you mean by "flagged". But all periodic tables are designed to show periodicity by placing groups in columns. They may or may not be labeled, but they are always displayed. It's what makes a periodic table "periodic".

• Light metals is fourteen times as popular as post-transition metals and reactive nonmetals, both of which we show.

  As I've mentioned elsewhere, I am very skeptical about using popularity this way. Frequency of occurrence is useful to determine what name to use for a particular element, or what elements should be included in a particular collection. It would also be useful to compare the frequency of different systems of categorization, but this cannot be determined by simplistic ngram comparisons.

YBG (talk) 06:07, 22 September 2020 (UTC)[reply]

@YBG: Yes, I agree about halogen. The WP PT showed it as a colour “zone” for ten years.

“Flagged” means to mark something in order to draw attention to it.

According to the COPTIC database the most popular categorisation scheme is either metal-metalloid-nonmetal (8%) or Ln-An (8%). The average number of categories is ~4½, within a range of 0 to 9. The 62 schemes are diverse.

Following the literature, the WP colour category table would just show metals; metalloids; nonmetals; Ln and An. That is not so informative. TMs merit a guernsey, as do NGs. That leaves the s-block; the metals between the TM and the metalloids; and the nonmetals between the metalloids and the noble gases. At this point, and in terms of the literature, the ngrams then have their place. Sandbh (talk) 13:30, 22 September 2020 (UTC)[reply]

re Sandhbh: I don't understand 'guernsey' here. re The WP PT showed it as a colour “zone” for ten years: true and trivial. (but why use "zone" out of the blue? Is that different from category?). Anyway, that discussion is available. I have not read a single argument against it recently but lamentations and qualified popularity claims. Also a Venn-category ("nonmetal halogens") is proposed for similar absent reason. And, of course, the set name halogen is already in use. -DePiep (talk) 15:58, 23 September 2020 (UTC)[reply]

@DePiep: Meriting a 'guernsey' means you are on the sports team, and get to wear a top with the team colours on it. I used "zone" as a vanilla way of referring to a set of elements without necessarily being concerned about whether they are a formal Group, or a category. For example, the end zone in American Football, or a red zone as a loose name for any area of concern. If I understand you right I am not proposing a Venn category spanning the nonmetals. Rather, I am proposing two sub-categories of reactive nonmetals: 1. Reactive (pre-halogen) nonmetals; and 2. Reactive (halogen) nonmetals. In other words, something along the lines of "Colour category PT: Proposal 2", below. Sandbh (talk) 00:14, 24 September 2020 (UTC)[reply]

Taxonomic periodic table

Extended content

@R8R, YBG, and DePiep: Further to the previous section, here is draft table for the lead of our periodic table article, followed by the current version.

I have temporarily abandoned the rare earth category. It seems like too much bother. Sandbh (talk) 02:50, 22 September 2020 (UTC)[reply]

@R8R, YBG, and DePiep: The third version retains the categories we have now. The intensity of the red shade for the AM has been toned down. The noble metals are denoted by a carat symbol. The pre-halogen reactive nonmetals are each flagged with a degree symbol = a circle of life; the associated note mentions alt-names found in the literature. The Group 17 marker has a dagger-note referencing F to I as halogen nonmetals. Sandbh (talk) 11:39, 22 September 2020 (UTC)[reply]

The circle further corresponds with the catenative tendencies of the nonmetals involved. Sandbh (talk) 23:00, 22 September 2020 (UTC)[reply]

Extended content

What grams are good for - and not

Imagine for a moment that we are not categorizing elements but some portion of the animal kingdom. Imagine further that there are no biologists talking about this issue. Implausible, I know, but bear with me.

At issue is whether we should have separate categories for platypus and echidna -- or a single category for monotremes.

What do the google grams tell us? Check it out here.

Platypus and eckidna are way more popular than monotreme, so of course we have two categories, not one. Right?

No, that is absurd.

Likewise, it is absurd to use ngrams to decide whether to combine AM & AM.

What good then are ngrams? Well, if we do decide to merge two groups into one category, it might be useful in deciding a name, by using something like this ngram. Of course one would have to determine if "active metal" is being used in the sense intended. And one would need to figure the right way to encode pre-transition. But i hope you get the point. Ngrams may help us decide a name of a category, but not whether something should be a category.

YBG (talk) 08:09, 12 September 2020 (UTC)[reply]

I see your point. While I don't disagree with it generally, I'd like to point out that I would not have brought up Ngrams if there were not enough difference, like in the case you mention. "Platypus" is ten times more popular than "monotreme" (based on the 2019 data) and "echydna" 3.5 times, which to me is a sign that the amount of occurrences of "monotreme" is not negligible. The difference between "alkaline earth metal" and "pre-transition metals" is three orders of magnitude, not one---that's a big difference and I'd say, it's telling enough.

I see "pre-transition metals" as a generic term. We also have other generic terms, say, "post-transition metals," so it's possible to have another in principle. However, "post-transition metals" has no non-generic alternatives whereas "pre-transition metals" does, and on basis of that we shouldn't add "pre-transition metals" to our fold of categories. That was my initial hunch to check Ngram, and I'd say I have my hunch confirmed as convincingly as that tool could.--R8R (talk) 09:19, 12 September 2020 (UTC)[reply]

re YBG. I greatly enjoy the more abstract, maybe mathematical, approach (met more than once here). I find it amusing (not really, worrying actually) that this thread refers to "popularity" of a wording. As if that is going to be an argument, or source even (I mistyped: artgument. lol). What happened to finding RS for a claim? As for tallying, this is the furthes we can go I'd say.

Then zoom out: in what discussion is this brought up? If I am reading all this right, renaming and reorganising categories. (Another weird approach I find: somehow trying to merge groups and categories; for & by their names even. Ouch for such aim).

In general: if a category is related internally strong, and externally weak: good. -DePiep (talk) 21:10, 12 September 2020 (UTC)[reply]

Allow me to add yet another reason I am skeptical about using ngrams to decide whether a particular collection of elements should be considered an enwiki category.

By ngrams alone we cannot determine much about the context. As DePiep concisely said, the relationship or similarity between elements of a category to other elements should be internally strong, and externally weak. There are three things we need to note about a collection to help us in this.

1. What elements are being discussed? In some cases this is trivial; in others, it requires a meta-analysis such as that at Lists of metalloids.
2. How are the internal similarities described? In particular, how strong are they?
3. How are the external comparisons described? In particular, what other collections are contrasted?

For example if we are wondering about the noble gasses, 1 and 2 are fairly obvious, but 3 is telling. In discussing the NG, does an author merely compare and contrast them to other groups? Then the article is discussing the NG as a PT group. But if an author compares the NG to larger collections of elements or even all other elements, then the article is discussing the NG as a higher level of the taxonomy, eg, as what we at enwiki call a metallicity category.

What about the AM (or AEM)? Again, 1 and 2 are obvious, but 3 interesting. If an author contrasts the AM (or AEM) to groups like the NG, AEM/AN, or group 3, then the author is discussing the AM (or AEM) merely as a group. Only if the author compares the collection to larger collections that are bigger than groups would I be willing to say the author is treating the AM (or AEM) as more than just a group, as something at a higher level of the taxonomy, like our enwiki metalicity categories.

My main point here is that such information - which I submit is critical for whether we should consider a group to be not just a group but also a metalicity category - such information cannot be deduced from ngrams.

This is hopefully a better and more complete explanation than my discussion of Australian megafauna above.

-- YBG (talk) 07:53, 21 September 2020 (UTC)[reply]

@YBG, DePiep, and R8R: From my reading of the literature, external comparisons of sets of elements is uncommon. That is due to the established existence of meta-properties such as metallic; nonmetallic; IE; EA; EN; standard reduction potentials; outer sub-shell configurations; differentiating electrons; and crystalline and molecular structures. There is no intrinsic need to compare or contrast sets of elements, since any particular set of elements can be implicitly placed within the overall scheme of things by reference to these properties without the need for benchmarking with other sets of elements.

@DePiep: Your category-fidelity criterion of related internally strong, and externally weak appears to have merit. The AM and AEM don't warrant a category, given the strong external relationship the AM and AEM have with one another:

--- Sandbh (talk) 01:39, 23 September 2020 (UTC)[reply]

Halogens

I'm unconvinced of the helpfulness of separating out the halogens .... they already are grouped together. Similarly, I don't see the advantage of having alkaline metals and alkaline earth metals as full-blown categories .... they already have recognition as groups. Thus, I'd have a reactive metal category. I know that the same logic could also be used to preclude a NG category, but if any group is unique enough to be distinguished as a full-blown category, it is the NG.

As to OR, yes, all of these things are attested to in the literature, but there are many, many categories in the liturature, not just the ones we've chosen. Where we come close to the line is in our elevating one particular scheme of mutually exclusive and jointly exhaustive categories to the prominence of our infoboxes. On balance, I think it is ok but I can respect those who think we've crossed the OR line.

YBG (talk) 06:38, 9 August 2020 (UTC)[reply]

​Well, the traditional aspect of teaching the periodic table is to contrast the alkali metals with the halogens. So that'd be a relatively strong consideration.

This supports keeping the alkali metals, and separating out the halogen nonmetals noting the focus on the latter is always fluorine, chlorine, bromine, iodine. We did not do this with our current table. IIRC that was because we weren't able to satisfactorily characterise the other nonmetals as something other than {other nonmetals}. So we decided that they and the halogen nonmetals would collectively be the reactive nonmetals.

Going back to our first ever periodic table, there certainly are lots of categories in the literature. The chosen colour categories were an outcome of a discussion in WP:ELEMENTS based on the most popular categories seen in the literature, with some hand-waving and confusion when it came to the leftover nonmetals. The latter train-wreck, as seen in the literature and the eight different categorisation schemes seen in our nonmetals article, resulted in the {other nonmetals} category, as there didn’t seem to be anything better at the time.

In our endeavours to nail the other nonmetals we've now gone full circle from {other nonmetals and halogens} → {polyatomic nonmetals and diatomic nonmetals} → {reactive nonmetals}. Now we have a putative YBG-rules-compliant categorisation scheme for going from {reactive nonmetals} → {coactive nonmetals and halogen nonmetals} that would fulfil the worthy intent of our predecessors.

The remaining consideration is that while the characterisation involved is robust, the actual descriptive category label {coactive nonmetal} is not recorded in a reliable source. Not yet, anyway.

On the mini-table seen in our info-boxes, I find the colour scheme to be a helpful navigational aid. Richey et al. (2010), writing on learning theory, support the use of colour to differentiate ideas and direct attention to key topics.

Richey, R.C., Klein, J.D., Tracey, M.W.: The instructional design knowledge base: Theory, research, and practice. Routledge, New York (2010)

--- Sandbh (talk) 23:38, 9 August 2020 (UTC)[reply]

The traditional pedagogy contrasting halogens with alkali metals says nearly nothing about the question at hand because both are groupa. A desire for consistency in our categorization does make that argument, but consistency could equally be used in favor of a reactive metals category. I strongly believe that only the noble gases are deserving of a monotypic category. It seems to me that one fewer category would make our system would be better pedagogicallly, better esthetically, better taxonomically, and better mnemonicly. Of course, when you discuss a given category, it would make sense that you begin by a group-by-group discussion. If such an approach works for the transition metals, then why not for the reactive metals and reactive nonmetals?

As a separate issue, we could reduce the number of categories by one more by adopting the term inner transition metals. This would have another advantage in eliminating the only horizontal boundary line. Its not quite as bad as summer time zones in Australia, but ...

In short, our current nine categories is quite unwieldy being at the extreme limit of the magic number

7±2

. Increasing it to ten is really too much, going in the wrong direction. I'd much rather see us go to eight or even seven.

--- YBG (talk) 04:55, 10 August 2020 (UTC)[reply]

PS check https://colorbrewer2.org to see how much more flexibility we have with fewer categories. YBG (talk) 05:13, 10 August 2020 (UTC)[reply]

@YBG: There is hope. I don't know how other members would feel about it:

               Noble gases
               He to Rn
Active metals           Halogen nonmetals
Groups 1-3, Ln, An      F to I
Transition metals       Coactive nonmetals
Most of them            H, C-O, P-S, Se
Post-transition metals  Metalloids
Ag, Sn, Bi etc          B, Si, Ge, As, Sb, Te
               Noble metals
               Ru, Rh, Pd, Os, Ir, Pt, Au

Eight categories. Symmetrical relationships. These can facilitate learning since fewer observations are required to describe the applicable system. Further, concepts that possess symmetry can be more easily grasped than those that do not (Randall 2006).

"Active metals" is in the literature. The noble metals are a subset of the transition metals (MacKay et al. 2018; Rayner-Canham 2018). I presume we will want to retain the popular notion of the metalloids being an intermediate category. That is fine. We can simply note that it has been known for over 120 years that metalloids have a predominately nonmetallic chemistry (Newth 1894; Friend 1914).

All categories meet the YBG rules. Note this is a consistently non-Group approach. That said, we additionally list the Group names along the top of each group as we do in the main body periodic table of our article of the same name. Ditto, we include the category names lanthanoids and actinoids to the left of the respective rows, as we used to do.

Winners all round. Eight consistent categories. Simpler colour scheme. No more tears over categorising nonmetals.

I note in the past we rec'd an objection to removing the alkali and alkaline earth categories.

PS: When discussing a category, you can start at the category level and examine its shared characteristics. Then you could examine the 18 groups from L to R (presumably) so you can track, among other things, the transition in metallic to nonmetallic behaviour. As well, where relevant you can examine the groups within each category. Much flexibility as to approach.

• Friend, J.N.: A Text-book of Inorganic Chemistry, vol. 1. Charles Griffin and Company, London, p. 9 (1914): "Usually, the metalloids possess the form or appearance of metals, but are more closely allied to the non-metals in their chemical behaviour"
• MacKay, K.M., MacKay, R.A., Henderson, W.: Introduction to Modern Inorganic Chemistry, 6th ed. Nelson Thornes, Cheltenham, p. 204 (2002)
• Newth, G.S.: A Text-book of Inorganic Chemistry, pp. 7 − 8. Longmans, Green, and Co, London (1894)
• Randall, L.: Warped passages: Unravelling the universe’s hidden dimensions. Penguin Books, London, p. 193 (2006)
• Rayner-Canham, G. Organizing the transition metals. In Scerri E., Restrepo G. (eds.) Mendeleev to Oganesson: A Multidisciplinary Perspective on the Periodic Table. Oxford University Press, New York, pp. 195–205 (2018)

--- Sandbh (talk) 06:40, 10 August 2020 (UTC)[reply]

So I'm trying to draw the periodic table with these color schemes. I have two questions. First, where does copper go? Transition metal I assume, but based on its position, it seems that it might be a post-transition metal. Second, what happens after bohrium? Is hassium a transition metal or a noble metal? Meitnerium? Copernicium? Oganesson? ― Дрейгорич / Dreigorich Talk 03:43, 11 August 2020 (UTC)[reply]

@Дрейгорич: Nothing else changes compared to our current table. Cu is TM, as are Bh and Hs. Anything after that is unknown properties. Sandbh (talk) 11:51, 11 August 2020 (UTC)[reply]

@Sandbh: Ah. Curious why hassium isn't considered as one of the noble metals then. It's right below osmium, which definitely is a noble metal. Hassium should be even more so of a noble metal. Or does the trend break down? ― Дрейгорич / Dreigorich Talk 14:56, 11 August 2020 (UTC)[reply]

@Дрейгорич: I suspect the reason why Hs isn't considered to be a noble metal is that we haven't so far had a way of flagging elements to show their predicted categories e.g with a circumflex^. If we did then I'd suggest Hs = noble^; Mt = transition metal^; Ds-Rg = noble^; Cn, Nh = unknown; Fl, Mc, Lv, Ts = post-transition metal^; Og = unknown. Sandbh (talk) 00:53, 12 August 2020 (UTC)[reply]

PS: I suggest colouring the noble metals the same as the transition metals. See here for an example of what I mean. Sandbh (talk) 00:58, 12 August 2020 (UTC)[reply]

@Sandbh: Huh. Any reason Mt isn't likely a noble metal? I think it would be a denser, super-radioactive version of iridium pretty much. Is there something in its chemistry that's predicted to stop it from being a noble metal? ― Дрейгорич / Dreigorich Talk 01:01, 12 August 2020 (UTC)[reply]

@Дрейгорич: Yes. Meitnerium is expected to about as noble as silver (the standard electrode potential for the Mt³⁺/Mt couple is expected to be 0.8 V, close to the +0.7993 V value known for the Ag⁺/Ag couple). Rayner-Canham (2018, p. 205) in, "Organizing the transition metals" says, "This author would contend silver is so much more chemically reactive…that it should not be considered as a 'noble metal.' " Sandbh (talk) 02:05, 12 August 2020 (UTC)[reply]

Huh. A minor surprise then. Didn't know that. Thanks for helping me learn something new. ― Дрейгорич / Dreigorich Talk 02:08, 12 August 2020 (UTC)[reply]

@Дрейгорич: Works both ways, coactively if you will. I think I learn something new just about every time someone posts here. Sandbh (talk) 05:24, 13 August 2020 (UTC)[reply]

Coactive terminology in the literature

About the term coactive nonmetal, the complementary term "coactive metal" is found in literature in the following senses:

• "…adding a coactive metal (such as Pt, Ir, or Rh metal)"
• "The same set of experiments was performed in presence of other co-active metal ions Fe ⁺², Fe ⁺³, Co ⁺², Ni ⁺², Mn ⁺², Cd ⁺², Ca ⁺², Mg ⁺²…".
• "It is of great interest and challenging to improve new catalysts that consist of any of those components and new active metal component (ie co-active metal, promoter)."

There are several other references in the literature to "co-active" elements, materials or substances, including manganese, iron, nickel, cobalt and plutonium.

It further transpires there is a field of organocatalysis that uses small organic molecules predominantly composed of C, H, O, N, S and P to accelerate chemical reactions. So there is nice overlap between organocatalysis, coactive nonmetals, and the {biogens} category of nonmetals.

Summarising, the coactive nonmetals are distinguished by their:

1. moderate net non-metallic character;
2. covalent or polymeric compounds;
3. prominent biological roles^¶;
4. proclivity to catenate i.e. form chains or rings;
5. multiple vertical, horizontal and diagonal relationships;
6. uses in, or as, combustion and explosives;
7. uses in nerve agents;
8. uses in organocatalysis; and
9. dualistic Jekyll (#2) and Hyde (#5−6) behaviours, thus, "coactive" ^_^

¶ such biological chemistry being only understandable in terms of the symbiotic use of the nonmetals involved, "symbiotic" meaning "characterized by or being a close, cooperative, or interdependent relationship" (c.f. "coactive"): Williams RJP 1981, The Bakerian Lecture, 1981 Natural selection of the chemical elements, Proc. R. Soc. Lond. B 1981 213, 361-397 (361, 396)

Is "coactive nonmetal" a neologism or is it a descriptive phrase, c.f. "coactive metal"? If there are coactive metals does this suggest there are coactive nonmetals? The other nonmetals category is well enough seen in the literature. The covalent-polymeric, biological, catenative, combustive/explosive, and organocatalytic properties of the nonmetals in this part of the periodic table are documented in the literature. Historically, the "other nonmetals" category is the most enduring nonmetal category used in the Wikipedia periodic table, until we started complaining about what a non-informative category name this was. Do we now have enough content, in pursuit of a better encyclopedia, to support a change back to a binary categorisation of the nonmetals as coactive (formerly other) nonmetals, and halogen nonmetals? I'll ask around. --- Sandbh (talk) 01:33, 10 August 2020 (UTC)[reply]

@Sandbh: I don't quite understand whether you propose a change for a new category scheme to be used now in en.wiki or not. I personally thought that this section started as a series of lighthearted jokes (I didn't have much to add but I liked how everyone was having fun) and have trouble understanding what it has evolved into since. Are you proposing a change or are you thinking out loud? I'd like to formulate my opinion, too, but for that I would need to understand what it is that I am to formulate my opinion about.--R8R (talk) 16:14, 10 August 2020 (UTC)[reply]

@R8R: Yes, I'm pitching a change to our scheme from reactive nonmetals, to coactive nonmetals and halogen nonmetals. It's funny how these things get started. You'll remember the other nonmetals saga, which resulted in our current scheme. At the time you said, "I see myself agreeing on a divide with two clear self-descriptive relevant terms, but throughout all of this time, we haven't found a single one." We now have such a divide with two clear self-descriptive relevant terms.

A consideration is that the adjective "co-active" is found in the literature as part of the phrase "co-active metals". But the phrase "coactive nonmetal" isn't. The closest we get is that coactive nonmetals have (organo-)catalytic applications; that coactive is a synonym for catalytic; and that coactive encompasses the various other synergic aspects of the coactive nonmetals. Oh, and it is pleasing that in going from reactive to coactive requires only two letters to change, by no more than three places in the alphabet.

One of the meanings of "other" is "existing besides". Synonyms for "besides" include "in conjunction with", (here conjunctive means, "relating to or forming a connection or combination of things"); conjointly"; and "jointly". So there is a pleasing link to the nature of the nonmetals in question.

See also my response to Dirac66, hereunder. Sandbh (talk) 07:47, 11 August 2020 (UTC)[reply]

I see. In that case, I will recall that my opposition back when we were establishing the term "reactive nonmetals" was based on that there was no well-known term to describe the division within the nonmetals other than the noble gases. In the absence of that, "reactive nonmetals" was the next best thing because it was fairly descriptive: these are nonmetals that commonly engage in chemical reactions, as opposed to the noble gases which don't. The word "reactive" is a part of the common language. A well-established term would be better but there isn't one, so we have to settle on that.

I am uneasy about the term "coactive metals". The thing is that I had never head the word "coactive" prior to this discussion and I thus didn't know its exact meaning, although I could guess. After writing this message, I genuinely had to check what this word meant. I take my own words with a pinch of salt since I am not the most potent English speaker, but I see that Dirac66 has similar concerns below.

So after (again, unironically) checking what the word meant, I learned it meant "acting in concurrence or together." With this knowledge in mind, I find it difficult to imagine that it will be easily understandable what the term means. I wasn't able to guess (which is worrying, too) but I just re-read the above to understand what was meant here. And unlike the rest of the terms (like "alkali metals" or even "reactive metals"), this term is not even about chemistry per se, which makes it rather doubtful that we want to use it as a part of the primary classification of the chemical elements. To me, these considerations are a deal-breaker.

I also think that "halogen nonmetals" is a rather deceptive term. We normally think of the halogens as of nonmetals, and I think it's going to be fairly common for common readers to not see the point why it can't be just "halogens." However, it can't, so the source of confusion is here to stay (yes, we can describe it but many people people won't click the link to find the explanation; they may not even guess a description is to be found behind that link). I think that bringing confusion isn't good for the purpose of having an encyclopedia for a common reader.

I think it's a fair attempt to renew our classification, but I'm afraid it's not fit for our purpose. That being said, this is not to say it can't be used at all (though I'd still be weary of having to intersect two independent terms "halogen" and "nonmetal" to get one).--R8R (talk) 15:25, 11 August 2020 (UTC)[reply]

@R8R: Thanks, it was a bonus to read your assessment that it’s a fair attempt to renew our classification. Things can only get better from there.

I'll attempt to carefully address your concerns.

1. No well established term for the division. That is not our concern. We have to deal with the literature as is. The most popular term is other nonmetals.

2. The term coactive is not understandable. Why are we applying a higher standard in this case? I agree, coactive is not a common term. Neither are alkali, alkaline earth, lanthanide, actinide, post-transition, and metalloid for our target audience of common readers. That is where wiki-links come into play. I do not concern myself if a common reader does or does not choose to click on a link.

3. Not about chemistry. The term "coactive" is found in the chemistry literature. It refers to catalysis. So, coactive nonmetals have (organo-)catalytic applications; coactive is a synonym for catalytic; and coactive encompasses the various other synergic, chemistry based aspects of the coactive nonmetals.

There is a further pleasing link to the nature of the nonmetals involved in that a subtle meaning of "other" is "existing besides". Synonyms for "besides" include "in conjunction with" (here “conjunctive” means, "relating to or forming a connection or combination of things"); “conjointly"; and "jointly".

4. Halogen nonmetals is rather deceptive. Common readers will not know what halogens are. On halogen nonmetals, this term is found in the literature. Common readers will not know this. They will have no reason to wonder why we don't just say halogens, in the same way we don’t just say alkaline earths.

The real issue, as I see it, is a gap in classification science terms. So, after applying the most popular categories found in the literature to the periodic table, what is leftover for the remaining nonmetals is other nonmetals.

Whereas a category name would normally be descriptive, other nonmetals is a non-defining-characteristic name.

In summary, while the category concerned already exists it's let down by its non-defining-characteristic name. It seems like a small step from "other" to "coactive".

All the properties of interest are set out in the literature, as is the "other nonmetals" category. Other nonmetals seemingly means nothing meaningful; coactive nonmetals may be unfamiliar but is rich with meaning.

It'd be funny to return to other nonmetals, which we should, since this is the most popular name for nonmetals in this part of the periodic table. I see no grounds for not doing so.

We do have a better descriptive phrase now, however. --- Sandbh (talk) 07:43, 12 August 2020 (UTC)[reply]

I have seen and read your message; not sure when I'll be able to write down a response; my apologies in advance in case I'm not able to do so quickly.--R8R (talk) 12:52, 13 August 2020 (UTC)[reply]

@R8R: I'll see if I can get around to drafting a nonmetal article based on other nonmetals, halogens, and noble gases. For the "halogen nonmetals", the oldest use of this term I've seen so far is from an 1885 Chemical News article. --- Sandbh (talk) 07:28, 14 August 2020 (UTC)[reply]

Here comes my response.

I suppose that we may ignore points 1 and 3 for now. My mind has been off this topic for a while now, and I can't be certain you're correct, but I can't claim the opposite, either, so I don't oppose those responses. Generally, this is why I offer myself as a sort of sanity check rather than a side of a discussion; the same also went for the last group 3 debate.

My greatest concern is point 2. I have been consistent about how there should either be a common term in the field or, in the absence of that, a term intelligible to a common English speaker. Say, "alkali metal" is very common; you learn it during the first year of your school chemistry classes. Same goes for AEM, Ln, An, TM, metalloid, and the noble gases. (The term "halogens," for that matter, would also fall into this category, and I assume this is why it was used in our classification for so long.) The term "post-transition metal" is intuitive for an English speaker (a metal that comes after a transition; it is precisely so, there is a transition to come after, and a metal in this category comes precisely after the said transition). What's left is the set of the non-noble nonmetals, which I suggested we define as "reactive nonmetals"---nonmetals that react (which, in fact, they do). We don't use the term "other nonmetals" solely on the account of its meaninglessness---you need to define the other terms first to see what's left.

I disagree that what the way I evaluate the suggested term is a higher standard. The standard has been the same. The term "coactive" doesn't appear to be understandable. I'd have my own reservations about this conclusion because it came from myself and I'm not the best English speaker out there---I learned the word "detergent" today, for instance---but another editor, whose English is probably better than mine, has said they hadn't heard it, either. Does it maybe somehow qualify as a professional term? I'm actually very willing to ask our fellow editors from

WP:CHEMS

to see what they have to say; I suspect that I'm right in my scepticism but I feel I can't claim that, so I'd gladly ask for more opinions. What would you say?

As for point 4. I assume that the common reader will know what a halogen is. It's an important consideration for me since I always try to have common readers in mind, so I'll expand on this.

The common reader I have in mind is a person who knows the very basics and that's pretty much it. The said basics of chemistry do include the term "halogen." I always write myself trying to make my texts as understandable as possible, but this sometimes requires too much explanation if I assume that the read doesn't know anything, and the complete explanation simply doesn't fit, so it turns out I have to assume some knowledge of the reader (or say that an article is not for them). In fact, the last time we had a discussion about this, you suggested I don't include an introduction to the superheavy elements to all respective articles because that's rather offtopic. Presumably you expected the common reader to know what the introduction had to say or say that the article wan't for them? What's the difference between that case and this one?

I also think that assuming that the common reader knows nothing we talk about anyway and all terms are on an equal footing is rather a disservice for the common reader. Some terms are better known than others. Even if they don't know them, they can look them up. If they won't look anything up, then they better learn a term they could say to someone who understand more and not hear in response, "never heard that term, where did you hear that?" We could deviate from this idea in principle if we weren't an encyclopedia that is meant to be a tertiary source.

coactive nonmetals may be unfamiliar but is rich with meaning -- that would be a fine rationale if you were to write your own book and you were thinking what terms to use. In Wikipedia, however, "unfamiliar" compounded with "uses a word that is uncommon in general" is a problem.--R8R (talk) 16:22, 15 August 2020 (UTC)[reply]

@R8R: Thank you.

Common reader. I take the common reader to be one of the people I meet on a day-to-day basis. Neighbours, friends, former work colleagues, coaching clients, social contacts, family. People who, these days, punch an unfamiliar term into WP rather than, as occurred in the old days, look it up in a hard copy dictionary. One of my neighbours is a chemistry teacher and he knows what I talk about. All the rest look at me dumbfounded. They usually recall what a periodic table is. Anything deeper than that is beyond them. Nonmetal—eh? Metalloid? Never heard it. Halogen? What's that? And so on.

The term coactive is not understandable. The word "coactive" is simple. It is made up the common "co-" prefix and the plain English word "active". Hence, for example, coaxial, co-operate, coauthor. I don't know of a simpler descriptive word for the orphan nonmetals. The word detergent, on the other hand, is not understandable. I would not know how to break if down (de-, tergent; what's a "tergent"(?); deter- gent?), although I know its meaning.

”Adding common prefixes or suffixes such as pre-, post-, non-, anti-, or -like to existing words to create new compounds can aid brevity, but make sure the resulting terms are not misleading or offensive, and that they do not lend undue weight to a point of view."

There is

Ask our fellow editors from

and asked why there is a need to change from the set {other nonmetals-halogens-noble gases}.

As I noted, WP:NEO does not apply here. Nor does WP:OR. The other nonmetal category exists in the literature. All the properties of interest are set out in the literature. No new ground in chemistry will be broken. The meaning of coactive is supported by reliable sources. The subject matter is notable.

An introduction to the superheavy elements to all respective articles. I suggested not including an introduction to this for the same reason we don't have an introduction to metals at the start of all respective articles. One can click on the first

reactive nonmetal

article; rather, the term links to the relevant part of the nonmetal article).

^ try looking up hatnote, hat note, or hat-note in the Oxford English Dictionary—you won't find it

^     *     *

I recall you supported a binary division of the non-noble nonmetals. We went with reactive nonmetals as we could not find a suitable term for the non-halogen nonmetals, aside from "other nonmetals", which nobody liked due to its meaningless nature. Well, now we have a suitable descriptive term.

"Other nonmetal", which by rights we should be using, is uncontroversial but uninformative. The logical alternative of "coactive nonmetal" is fully informative and encompassing, and does not breach WP policy. It may cause cause a ripple of excitement for unproductive and unfounded reasons—reasons that do not fundamentally have anything to with building a better encyclopedia. By "encyclopedia" I mean a reference work or compendium providing summaries of knowledge from all branches, rather than a reference work missing some summaries due to needless terminological confusion.

I think I've addressed all your concerns. Please let know of your thoughts. --- Sandbh (talk) 06:04, 16 August 2020 (UTC)[reply]

Again, I apologize but my response probably won't be very quick.--R8R (talk) 18:01, 18 August 2020 (UTC)[reply]

@R8R:. Sandbh has abandoned "coactive nonmetal" as a category name, now preferring "pre-halogen nonmetal".YBG (talk)

@YBG and R8R: Sort of abandoned. In my head it's like other metals → post-transition metals → frontier metals. The corollary is other nonmetals → pre-halogen nonmetals → coactive nonmetals. Sandbh (talk) 01:01, 19 August 2020 (UTC)[reply]

Term succession

@Sandbh: Although I see the name "coactive metals" has been abandoned, I still think it may be useful to reply to Sandbh's previous points. The usefulness may be in sharing the thinking why I pass judgment on different names one way or another.

Common reader: While I agree with what you're saying here, it is still not useful to those readers who will read the article as to people who have no clue about chemistry in general. First of all, my general assumption is that it's likely you have at least an interest in chemistry or some sympathy to it if you're really going to read an article on a grouping of elements or a Chemistry section of an article on an element. The term "common reader" in this context refers to people who don't have much beyond that but who do have that much. Second, while the said common reader is the primary audience, there is also the need not to have professionals scoff at what we write. If they all turn in saying they had never heard a term, then that term is a no-no. The way out of this, as I have mentioned, is descriptory phrases. I think it's easy enough to see how "post-transition metal" is such a phrase. The same goes for "reactive nonmetals" if you note that the only other category of nonmetals is the set of noble gases, which are famed for being unreactive. I doubt the same goes for "coactive metals."

The term coactive is not understandable. I sustain it is not, at least not for me. While the etyomology is clear from the mere look at the word (co- + active), the same does not necessarily goes for its meaning. Whereas the word "coauthor" is easily seen as the sum of co- and author, I've never thought the same way about, say, the word "cooperation." As one way out of this confusion, I'd suggest you try to explain in one short phrase what the term means by referring to the words used in it. A "post-transition metal" is a metal that comes after a transition. A "reactive nonmetal" is a nonmetal that commonly engages in chemical reactions. What's a coactive nonmetal then? Maybe there is an answer, but I would like to hear it if we were still discussing that term. It would help a lot.

Now as for the new term, I find it rather strange to have a pre-halogen category that has six member whereas the halogen category has only four. I am also somewhat uneasy about having to intersect the terms "halogen" and "nonmetal." While you mentioned a 1885 source doing that, that was plain tautology back then when astatine wasn't known---I rather doubt it was meant to be a term. Regardless, neither of these concerns is a dealbreaker; we could live with that. I'd prefer we didn't for the reasons I have just outlined, but that is a mere personal preference and I don't feel very strongly about the whole issue of categorization as long as we have names that do not immediately call for an objection.

By the way, I don't recall supporting a binary division. However, there's a great number of things I don't recall, so this remark is not a claim of the opposite. I may have written something along the lines of "we could have it in principle and that wouldn't be too bad." I thought you had quoted me saying that here and that quote could maybe rule out this possibility, but I can't find that quote.--R8R (talk) 09:20, 22 August 2020 (UTC)[reply]

@R8R: I agree with you about a descriptive phrase, as far as this is preferable to a “neologism”.

As I see it, "coactive nonmetals are noted for their catalytic, catenative and covalent associations" (or something like that). Although it is a moot question, how does that seem?

Pre-halogen nonmetals are precisely that, no more, no less. I cannot do anything about the fact that they are positioned before the halogens, and that there are four halogen nonmetals (or six halogens, from F to Ts, if you prefer) and seven pre-halogen nonmetals.

Intersecting halogen and nonmetal: In an Introduction to chemical principles, Fernandez & Whitaker (1975, p. 197) wrote:

"It was seen that the noble gases form a logical "buffer" zone of relatively unreactive elements separating the very reactive alkali metals and the very reactive halogen nonmetals."

In our Block (periodic table) article we say:

"Metals of the s-block form ionic compounds with the halogen nonmetals in group 17."

Here’s a 2020 example using the term halogen nonmetal:

"Most semiconductor NCs are composed by (n −1)d10 metals of groups 11−15 (with empty or filled ns orbitals, such as Cu, Ag, Zn, Cd, In, Pb, and Bi, among others) and chalcogen, pnictogen, or halogen nonmetal atoms…"

doi:10.1021/acs.accounts.0c00204

.

The fact that the halogens have a well-recognised name and that the “other nonmetals” don’t is presumably a reflection of the seeming diversity of the latter e.g. lightweight hydrogen; fecund carbon; noble nitrogen; powerhouse oxygen; smelly sulfur; pyrophoric phosphorous; and mysterious selenium. Even so, at least their connection with organic processes is reasonably well known, I would’ve thought.

You stated your support for two categories of reactive nonmetals in archive 30, Dec 2017:

"While I am eager to be proven wrong, I continue to think that there is no good divide at all. I see myself agreeing on a divide with two clear self-descriptive relevant terms, but throughout all of this time, we haven't found a single one."

As you opined, the only thing holding things up was a name better than "other nonmetal", which we where unable to do at that time and for the preceding how every many years before that. Sandbh (talk) 13:16, 22 August 2020 (UTC)[reply]

Over to you, товарищ. --- Sandbh (talk) 13:16, 22 August 2020 (UTC)[reply]

Concise definition

Coactive nonmetals: Coactive ("acting together") refers to their behaviours in organocatalysis; linked geobiochemical cycles; tendency to form covalent or polymeric compounds; catenative proclivities (ring and chain forming); and dualistic Jekyll (biogenic) and Hyde (explosive and combustive) properties and applications.

Other nonmetals

A comment on the term "coactive nonmetals". I have never seen the word “coactive” before today in any context, so I am naturally worried about whether its use should be disallowed as “original research” which is not supposed to be on Wikipedia.

Sandbh has found some examples of chemical uses of the word “coactive” without the noun nonmetals. However, the word seems to be used in specialized contexts such as catalysis, and not in the sense proposed here of a general descriptor for certain columns of the periodic table.

In general, I think Wikipedia is supposed to indicate the vocabulary used in most other sources, which here means chemistry textbooks and chemistry journals. And it seems to me (without really checking the sources myself I admit) that the usual term is just “other nonmetals”, as in “halogens, noble gases and other nonmetals”. So why do we need to replace this phrase? Dirac66 (talk) 18:29, 10 August 2020 (UTC)[reply]

@Dirac66: Thank you.

Yes, you're right, the most popular form is other nonmetals, in the absence of anything more meaningful. Lesser known names for the nonmetals occurring in this part of the table are:

• biogen nonmetals;
• CHONPS nonmetals;
• intermediate nonmetals;
• light nonmetals;†
• organogen nonmetals;
• orphan nonmetals;‡ and
• quintessential nonmetals.

† e.g. Williams RJP 1981, The Bakerian Lecture, 1981 Natural selection of the chemical elements, Proc. R. Soc. Lond. B 1981 213, 361-397 (365)

‡ In a juvenile-level book called, Science of everyday things: Real-life chemistry (Knight 2002, Gale Group), which divides the nonmetals into noble gases, halogens, and "orphan" nonmetals. I laughed when I saw it. In a funny way, if only it wasn't so tragic, it is marginally better than other nonmetals.

Previous discussions in our project have centred on the meaningless nature of the "other nonmetals" label.

It's puzzling that, in the literature, the metals start out loud and proud, as alkali metals; alkaline earth metals; Ln/An; transition metals; and then fade away with the sixteen different names for the post transition metals. Then there are the reasonably well established metalloids, even though their boundary can move around a bit. And then we come to the first of the really well recognised nonmetals in a train wreck of classification science. They may as well be called the schemozzle nonmetals. After them, as you observed, follow the well-known halogen nonmetals; and the noble gases.

On why we need to replace the phrase "other nonmetals", I feel the answer is because it is unhelpful; poor classification science; does a disservice to chemistry in this part of the periodic table; and a better solution is available. The situation is as like standing back and saying a good job wad done with categorising most of the periodic table, with the exception of the leftover, other, or remanent nonmetals. The result is what Zuckerman and FC Nachod (1977, preface) said i.e. “The marvellous variety and infinite subtlety of the non-metallic elements, their compounds, structures and reactions, is not sufficiently acknowledged in the current teaching of chemistry” in Steudel's Chemistry of the nonmetals.

I do not see any OR. All the properties involved, including the recognition of H, C-O, P-S, Se forming a category are in the literature. Maybe there is smidgeon of WP:BOLD. I guess a chemist who saw "coactive nonmetals" might wonder what they are if they weren't familiar with the "coactive" adjective. They might look up coactive in a dictionary to see what the term means, or they might look at the nonmetal article, and see we are referring to the other nonmetals. At which point they might say, ah the term is unfamiliar, but the category, as other nonmetals, is. Now I get it. Much better than "other" which tells me nothing.

Could you please also see my response to R8R, above. Sandbh (talk) 07:47, 11 August 2020 (UTC)[reply]

@Dirac66: It seems like a completely generic term for the other nonmetals H, C, N, O, S, P, Se would be pre-halogen nonmetal as that is what they are, no less no more. Your thoughts? thank you, Sandbh (talk) 06:41, 21 August 2020 (UTC)[reply]

Biogeochemical cycles

I'm a bit gobsmacked to learn that we have articles on the following biogeochemical cycles:

1. Hydrogen cycle; 2. Carbon cycle; 3. Nitrogen cycle; 4. Oxygen cycle; 5. Phosphorus cycle; 6. Sulfur cycle; 7. Selenium cycle

I'd never heard of 1, 5 and 7, the last one especially. Who'd've thought?

Wow! --- Sandbh (talk) 08:05, 18 August 2020 (UTC)[reply]

Past, present, future(?) categories

Looking ahead

Here's what I have in mind:

Metal					Metalloid	Nonmetal
Alkali metal	Alkaline earth metal	Lanthanoid	Transition metal	Post-trans- ition metal		Coactive nonmetal	Halogen nonmetal	Noble gas
		Actinoid

Aesthetically, Ln over An is more pleasing. --- Sandbh (talk) 07:13, 16 August 2020 (UTC)[reply]

re the aesthetical note: I don't think this is an aesthetic freedom. If the bottom row has these two stacked, this expression should have a meaning, since it introduces a new distinction. -DePiep (talk) 19:21, 9 September 2020 (UTC)[reply]

Where we've been; where we could be

In graphical form, loud and proud:

— Colour category history 2002−2020—
 

2002	Rationale given at the time	ca. 2003−2013	2013−2018	2018	Proposed	Result
Alkali metal	very reactive and therefore dangerous = red	same	same	same	no change	Alkali metal
Alkaline earth metal	nice earthy colour = easy to remember					Alkaline earth metal
Lanthanoid	chosen arbitrarily					Lanthanoid
Actinoid						Actinoid
Transition metal						Transition metal
Metal	true metals are closest in colour to grey	Other metal/Poor metal	Post-transition metal			Post-transition metal
Semimetal	intermediate colour between above and below	Metalloid	same			Metalloid
Nonmetal	elements most essential to life; most life on Earth measured by biomass is photosynthetic, and chlorophyll is green	Other nonmetal	Polyatomic nonmetal (C, P−S, Se)	Reactive nonmetal	Coactive nonmetal	Coactive nonmetal
Halogen	fluorine gas is yellowish as are many precipitates of halogens	Halogen (inc. At)	Diatomic nonmetal (H, N, O, F−I)		Halogen nonmetal	Halogen nonmetal
Noble gas	non-reactive for practical purposes; light-blue is soft and soothing; aka aerogens = blue sky (Sandbh contribution)	same	same	same	no change	Noble gas

---

Sandbh (talk) 07:13, 16 August 2020 (UTC)[reply]

The colors are (better: should be; see the original AM motivation for red) independent of the category content, and independent of cultural meaning. And we should strive to enhance that. That said, some improvements are needed, e.g. in color contrast, improving re colorblindness, and differentiation say recognisable between Table <--> legend, clear between-category border-difference. For clarification of current ideas indeed one can use current colors reassigned. Number of proposed categories should not be determined by color(-limitations, -goals). If the PT should have 14 categories, I think coloring them is the least problem.

IOW: go ahead with the proposal development, don't be bothered by colors. DePiep (talk) 18:43, 9 September 2020 (UTC)[reply]

Observations

• There are no
  WP:OR violations, per the chat R8R
  and I are having.
• @YBG: On 7±2, there is a little less to this than meets the eye. From the proposed legend in the Looking ahead subsection it is rather 3 (5-1-3) as in metal-metalloid-nonmetal, and within those three bundles chunks, {AM, AEM, La/An, TM, and PTM}, {Metalloids}, and {CN, HN, and NG}. 7±2 is thereby observed, similar to the rooms in a house memorisation technique. This is better taxonomically and mnemonically.
• The YBG rules are met.
• The green of the other nonmetal-coactive nonmetal category is very appropriate. For that matter, I like the yellow of the halogen nonmetals, and the blue of the noble gases (it looks turquoise on my monitor).
• The other nonmetal category exists in the literature. All the properties of interest are set out in the literature. No new ground in chemistry will be broken. The meaning of coactive is supported by reliable sources. The subject matter is notable.

--- Sandbh (talk) 07:13, 16 August 2020 (UTC)[reply]

Scheme royale

Legend 1: Periodic table categories

Metal					Metalloid	Nonmetal
Alkali metal	Alkaline earth metal	Lanthanoid	Transition metal	Post-transition metal		Pre-halogen nonmetal	Halogen nonmetal	Noble gas
		Actinoid	Noble metal ✣

This will address any residual concerns to do with "coactive nonmetals".

I've added an optional "noble metal ✣" sub-category of transition metal. The alchemical looking four balloon-spoked asterisk is to distinguish the noble metals in our main periodic table, thus e.g. Pt ✣, Au ✣. The actual positioning of the asterisk within a noble metal's PT box is flexible, having regard to coding and design considerations.

In our info boxes a noble metal would be categorised as Transition (noble) metal.

Figure 1: The eightfold way (category counterpart map)

	Noble gas
Active metal   Alkali metal   Alkaline earth metal   Lanthanide   Actinide	←↑↓→	Halogen nonmetal
Transition metal		Pre-halogen nonmetal
Post-transition metal		Metalloid
	Noble metal

Table 1: Alt-category names

Active metals	Hyper metals
Transition metals	Working metals
Post-transition metals	Poor metals
Noble metals	High society metals
Metalloids	Junior nonmetals
Pre-halogen nonmetals	Respectable nonmetals
Halogen nonmetals	Psycho nonmetals
Noble gases	Cup of tea nonmetals

The symmetrical relationships seen in Fig 1. can facilitate learning since fewer observations are required to describe the applicable system. Further, concepts that possess symmetry can be more easily grasped than those that do not.

Students or instructors who enjoy more visceral distinctions may enjoy category names with attitude, as shown in Table 1. --- Sandbh (talk) 01:32, 17 August 2020 (UTC)[reply]

Comments by YBG

1. Number of categories:
   7±2
   . It is not 5+1+3 as Sandbh suggests, but more closely akin to 6+1+3 because you are using two colors for the inner transition elements. And, I would submit, because we have a unified periodic table with a unified color scheme (rather than three separate tables, metals, metalloids, and nonmetals), what you are proposing is not even 6+1+3 but rather a simple 10.
2. Categorization (a): Leftover category. Your idea to use *​coactive nonmetals eliminates the leftover nature of the category name but it does not change the fact that the leftover nature of the category itself. I strongly suspect that in the treatment of nonmetals, this category is universally treated as the last nonmetal category to be treated. This strongly suggests that whatever in-category similarities and between-group dissimilarities exist, the primary distinguishing feature is that these are NNNHNM - Non-noble, non-halogen nonmetals. Trying to find a synonym for the NNNHNM does not change the fact that this category is a hat-trick of left-over-ness.
3. Categorication (b): Good taxonomy. (or do the halogens need to be both a group and a category). It seems to me that much of the argument for dividing the reactive nonmetals here at WP:ELEM and in the literature is the desire to talk first about the halogens and then talk about the rest. I strongly believe that only the noble gases deserve to be a monotypic category. Otherwise, why stop there? Why not have chalcogen nonmetals, pnictogen nonmetals, carbon group nonmetals, and the comparable metalloid and metal categories?
4. Nomenclature (a): Coactive. This is a term that is never used non-technically, and, if I understand correctly, only rarely in a technical context, and that with a completely different meaning. For this to be even considered, the following analogy would need to be true:

   coactive metal : metal :: *​coactive nonmetal : nonmetal

   I'm willing to be corrected, but by my understanding of the information presented, this analogy does not hold. I note that this analogy is IMO a necessary but not sufficient condition for using the term.

5. Nomenclature (b) Good naming. The best names are those that are commonly used and meaningful in both technical and non-technical contexts, but at a minimum they should be commonly used in one or the other. "*​Coactive nonmetal" fails on both counts; the adjective "coactive" is only vaguely familiar and that only in a specialized technical context. Contrast this with the other category names (pun intended).

Category	To the professional	To your non-technical neighbor
Alkali metal	Term commonly used	Adjective vaguely familiar, but with slight difference in meaning
Alkaline earth	Term commonly used	Adjective vaguely familiar, but with slight difference in meaning
Lanthanoid	Term commonly used	Term totally meaningless
Actinoid	Term commonly used	Term totally meaningless
Transition metal	Term commonly used	Adjective understandable, meaning identical (but begs question, "between what and what?
Post transition metal	Understandable but not commonly used	Adjective understandable, meaning identical (but begs question "after what transition?")
Metalloid	Term commonly used	Term totally meaningless
Reactive nonmetal	Understandable but not commonly used	Adjective understandable, technical & non-technical meanings identical
Noble gas	Term commonly used	Adjective vaguely familiar, but with slight difference in meaning
Other nonmetal	Term commonly used (but has no meaning)	Term completely understandable, technical & non-technical meanings identical
Coactive nonmetal	Term not commonly used, never in this context	Term completely meaningless

(If there is any disagreement on the correct values in this table, please let me know and I will correct them)

Even the much-maligned "other nonmetal" comes out better than "*​coactive nonmetal" in this regard. It is frequently used in the literature, and its meaning (such as it is) is clear to both technical and non-technical audiences, but as WP:ELEM previously agreed, it is absolutely non-descriptive from both a technical and non-technical perspective.

I am quite content with the status quo, which was attained after at least two voluminous mega-discussions. I am certainly not convinced that a change is warranted, but if it is, I think it should be in the following direction:

Reactive metals Alkali metals Alkaline earth metals

Inner transition elements Lanthanides Actinides

Transition metals

Post-transition metals

Metalloids

Reactive nonmetals

Noble gasses

I am not agitating for this change, merely stating that I am far more comfortable with a change in this direction than in the direction proposed by Sandbh. YBG (talk) 02:15, 17 August 2020 (UTC)[reply]

Sandbh response 1&2

@YBG: Thank you. I'll respond shortly. In the meantime, since I expect I will abandon coactive nonmetal in favour of pre-halogen nonmetal could you please let me know how you feel about the SR proposal? We're close in our thinking. I believe I do like the (re)active metals and the inner transition metals. Sandbh (talk) 02:42, 17 August 2020 (UTC)[reply]

That eliminates my reason #4 and changes reason #5. As a category name, I'd rate pre-halogen as slightly worse than post-transition. One question, is this term ever used in the literature? How does its frequency compare to post-transition metal or reactive nonmetal, the two category names we have that aren't frequently used?

And of course, this name change does nothing to my reasons 1, 2, and 3. YBG (talk) 03:19, 17 August 2020 (UTC)[reply]

@YBG: I've addressed your reasons 1, 2 and 3 below.

Yes, the term pre-halogen is a real word. The main references are to the pre-halogen era of lighting (you'll find this expression in our Headlamp article); and I saw a reference or two to pre-halogen sedimentation, in a geological sense. I presume this is a reference to non-saline deposits.

It’s good to see ^_^ that in the pre-halogen era, lighting was provided via a pre-halogen nonmetal, carbon ^_^ So that gives us a pre-halogen era pre-halogen nonmetal = PHEPHM ^_^ Sandbh (talk) 09:07, 17 August 2020 (UTC)[reply]

Its frequency compared to post-transition metal or reactive nonmetal is insignificant. I feel this is not a significant concern. "Halogen" is widely recognised (by chemists), as is the plain English prefix "pre-" (prehistoric; a pre-nuptial; pre-natal classes; pre-school/care). Pre-halogen nonmetal is more informative than "other nonmetal". Given the hoi poloi of category names for nonmetals in this part of the periodic table, we have discretion on how to proceed, as provided for by

WP:MOSWTW

.

I feel that "reactive nonmetals" obscures information that is already in the literature about the discrete shared properties of nonmetals in this part of the periodic table e.g. the halogen nonmetals' uniformly high IE, EA and EN values, unlike the pre-halogen nonmetals. In the context of a better encyclopaedia, merging the two categories of NNNM represented a retrograde step. I signed up to it at the time out of dissatisfaction with the "other nonmetals" category. That said, we did not know then what we know now.

We will now lose nothing by splitting the reactive nonmetals. We will rather gain a much superior treatment and appreciation of the nature of the nonmetals involved. Nothing else changes. That is why I'm advocating for change.

Please let me know if you have any outstanding concerns.

--- 08:17, 17 August 2020 (UTC)

1. I feel we could agree(?) the categories look like this…

1	1	1
6	1	3

…where the top row is metal | metalloid | nonmetal. By chunking, the

7±2

rule is satisfied.

2. Yes, I agree it is a leftover category name (rather than a leftover category of nonmetals). That said, all the shared characteristics are set out in the literature. Yes, I agree they are NNNHNM, hence the proposed category name pre-halogen nonmetal which is exactly what they are.

3. We don't use those group category names as there would be too many categories. As well, our categories are designed to show the L-R transition in metallic to nonmetallic character.

4.–5. No comment as I'm moving away from this term.

This is what you have now:

	Noble gases
Reactive metals Alkali metals Alkaline earth metals	←↑↓→	Reactive nonmetals F-I
Inner transition elements Lanthanides Actinides
Transition metals		H, C-O, P-S, Se
Post-transition metals		Metalloids
	Noble (transition) metals

The Ln and An are "reactive" too. Their standard electrode potentials range from about −1.8 to −2.8; the group 1–2 metals run from about −1.8 to −3.0. The "reactive" sense you are referring to is better captured by "active" metals.

I support a merge of the AM and AEN. I ask for your support for splitting the reactive metals, which is good classification science, and has been the predominant presentation in our PT. We only merged the NHNNNM out of dissatisfaction with the other nonmetal category name.

I see you have since replied, so I'll have a look at that next. --- Sandbh (talk) 07:03, 17 August 2020 (UTC)[reply]

YBG reply

My comments:

• re 1. Number of categories. We want to color the entire periodic table with a single color scheme. This in and of itself means that we should strive to have the unchunked number of categories close to the ideal seven. But even more than this, I submit that we actually do not chunk these categories, Do we actually chunk these categories? Or do we generally discuss them all together? In what context(s) do we discuss the categories? Most frequently, the context is discussing all of the categories together. Slightly less frequently, we discuss a single category in and of itself. We almost never discuss the metal categories (or the nonmetal ones) by themselves apart from discussing all of the categories, metal, metalloid, and nonmetal alike. From this I conclude that we do not actually chunk these categories into three mega-categories but treat them together.
• re 2. Left-over-ness. I think you have missed my point here. My main point is that the category itself is a leftover category. I used the left-over-ness of the category name as evidence of the left-over-ness of the category itself. When WP used the leftover name "other nonmetal", we were showing that we considered the category itself to be a leftover category. If we adopt the non-leftover name "pre-halogen nonmetal", we are showing that we consider the category to be a non-leftover category. But what does the literature show? The overwhelming use of the leftover name "other nonmetal" testifies that the literature overwhelmingly treats the category as an "(e)-none-of-the-above" leftover category. Having WP change the name we use would not change the testimony of the literature as to the nature of the category. At issue here is how much within-group similarity there actually is.
• re 3. Taxonomy aka classification science. Again, my post failed to get the point across, causing you to focus on a relatively minor point. My main point here in whatever context we are, if we want to discuss the halogens, we do not need a halogen category to support this discussion, as we already have a halogen group. The term "Reactive nonmetals" does not obscure halogen info in the literature any more than "transition metal" obscures information about the iron group or the coinage metals.
• re 4. & 5. Now moot
• re 6. Distractions. (a) AM+AEM. I’ll happily reject the (re) prefix; "active metal" seems better than "reactive metal". But I prefer to treat AM+AEM as a separate issue rather than engaging in logrolling. (b) And by the way, I don't find your circular presentation that includes noble metals to be very helpful in this discussion. The chart is interesting and would be improved with the PTM on the right side, but IMHO it is a distraction in this discussion.

YBG (talk) 20:05, 18 August 2020 (UTC)[reply]

@YBG: 1. Number of categories. I suggest it isn't a matter of how we do or do not chunk or do or do not discuss the categories together. Rather it is a question of catering for the common reader of our encyclopedia, drawing on the literature. That is why, in my opinion, our legend is constructed the way it is, with the three major categories along the top, broken down into metal, metalloid, and nonmetal (sub)categories. That is consistent with the way chemistry is taught, with its top level focus on metals and nonmetals or metals, metalloids, and nonmetals. From there each of these major divisions are further explored, consistent with the application of chunking in learning theory (I speak here with benefit of an academic background in learning and development). I support you with your request for a merge of the AE and AEM. I have no strong concern about a separate category for the noble metals, even though it looks nice. That will leave us with eight categories, four metallic and four nonmetallic:

Re(active) metal
Inner transition metal
Transition metal
Post-transition metal
Metalloid
Pre-halogen nonmetal
Halogen nonmetal
Noble gas

A 4+4 arrangement is pleasing.

2. Left-over-ness. I follow you. This is a good example of the limitations of post-by-post chat.

The situation is analogous to the post-transition metal category and its 16 alternative category names, including other metals.

The existence of the metals involved is not in question. All the properties involved are set out in the literature.

The nonmetals involved have 10 or so alternative category names. If I may clarify something you said, the literature does not "overwhelmingly" use the expression other nonmetals. Rather, this seems to be the most common term of the alternatives, similar to the leading horse in a horse race, with a couple of other contenders not out of reach. If we are true to the literature we should in fact have an other nonmetals category! From a bad field I feel a generic category name in the form of pre-halogen nonmetals is preferable and acceptable. I did contemplate calling them the geobiochemical nonmetals. ^_^

The existence of H, C-O, P-S, Se as a category is not in question. All the characteristic properties involved are set out in the literature.

I've set out their remarkable within-group properties before. The pre-halogen nonmetals feature a remarkably rich array of shared characteristics. Summarising, they are distinguished by their:

1. moderate non-metallic character (IE, EA, EN)
2. covalent or polymeric compounds;
3. prominent (and linked) biogeochemical roles, each having individual "cycle" articles—unlike the other ^_^ nonmetals
4. proclivity to catenate (form chains or rings);
5. multiple vertical, horizontal and diagonal relationships;
6. uses in, or as, combustion and explosives;
7. uses in organocatalysis; and
8. dualistic Jekyll (#2) and Hyde (#5) behaviours.

3. Taxonomy aka classification science. The halogens may be discussed in two ways. First as group 17. Second as the four nonmetals (F−I) and one metal (At). Please bear in mind our periodic table is not a groupic table. It is a metallicity table. That said, we include the group names along the top, in order to provide a flexible approach. The halogen category by itself, obscures the nature of astatine as a post-transition metal. That is not an issue for the transition metals: they are all transition metals. Merging the halogen nonmetals and pre-halogen nonmetals hides the nature of the pre-halogen nonmetals.

6. Distractions. (a) That is good. Yes, I'll support a combined AE and AEM category as a separate issue. (b) I feel the circular presentation is helpful since it's something we can't do so well now. I say this as the pattern involved facilitates teaching and learning the periodic table; fewer observations are required to describe the applicable system; and concepts that possess symmetry can be more easily grasped than those that do not (Randall L.: Warped passages: Unravelling the universe's hidden dimensions. Penguin Books, London, p. 193 (2006)).

Looking forward to your further consideration of these interesting matters. Sandbh (talk) 03:53, 19 August 2020 (UTC)[reply]

I recognize that it is a minor point, but I take issue with your statement that our enwiki PT is not "groupic". It would be fair to say that PTs discussed in § Periodic ziggurat of the elements and § A partially disordered periodic table are "non-groupic", but not "our" PT. Yes, our color scheme is not "groupic", but any PT that displays each group in a column by itself could be considered "groupic". But perhaps I misunderstand what you mean. And as I say, I recognize that this is quite a minor point, and not I believe relevant to the main point here, which is our disagreement about the wisdom of isolating the halogens from the remainder of the nonmetals. YBG (talk) 05:40, 1 September 2020 (UTC)[reply]

Septenary heterogenous pre-halogen compounds

The pre-halogen nonmetals are capable of forming these. A simpler example is C₂₀H₂₆N₄O₁₀PSSe. I was surprised to learn that the chemical composition of the VX nerve agent is C₁₁H₂₆NO₂PS.

The first discovered nerve agent was tabun or GA, of composition C₅H₁₁N₂O₂P. Among the V series successors, VX is the most studied: C₁₁H₂₆NO₂PS. The selenium analogue of the VE nerve agent is selenophos C₁₀H₂₄NO₂PSe. This is more potent than VX =:ox

On the one hand the PHN sustain life; on the other they let us play with fire.

--- Sandbh (talk) 07:15, 23 August 2020 (UTC)[reply]

Twelve categories

By Dalby (2020) here:

s block • AM • AEM

f block • REE (Ln) ± • An

d block • TM (REE): Sc, Y • TM • TM (precious metals)^

p block • Post-transition metals • Metalloids • Polyatomic nonmetals • Diatomic nonmetals • Noble gases

^± La-Lu

^ rhenium, PGM, coinage metals, and mercury

@YBG, R8R, and DePiep: Twelve categories seems like a lot. That said, the author has provided two ways to chunk things down: by block or by metal-metalloid-nonmetal. So that's OK.

The way they have flagged the REE is interesting, given RE/REE/REM is nearly three times more popular terminology than lanthanides.

The precious metals category does not have so much relevance, being a little too diverse as such. Still, it does show the TM can be chunked down into more manageable parts:

Legend 2: Periodic table categories

Metal					Metalloid	Nonmetal
Alkali metal	Alkaline earth metal	Rare earth metal	Transition metal (ρ, ✣)	Post-transition metal		Pre-halogen nonmetal	Halogen nonmetal	Noble gas
		Actinoid

ρ Transition (rare earth) metal: Sc, Y, La

✣ Transition (noble) metal: Ru-Pd, Os-Pt, Au

Yes, I am proposing we replace the Ln category with the REM category, including showing Sc-Y-La as transition (rare earth) metals. --- Sandbh (talk) 00:16, 20 September 2020 (UTC)[reply]

@Sandbh: I think that the idea has its merit but Wikipedia is not the right place for such a proposal.

We use non-overlapping categories. The major advantage of that is that it's easy this way to distinguish groups and the scheme doesn't look too difficult to understand. If our major scheme will have first and secondary category notation, it will be more complicated, and that's a very big disadvantage. This will work poorly with a big table unless a person specifically thinks they'd love to gaze at the PT and it will probably be even worse with our small tables like the one in the infobox. Another disadvantage is loss of the lanthanide-actinide parallel (leading to the obvious question why it is not there because everyone who knows about the actinides knows equally well about the lanthanides). The advantage is not clear for me: it's safe to say everybody who understand "rare earth metal" understands "lanthanide" and doesn't find it any less intelligible, and vice versa.

I would not say that Dalby's proposal helps manage the big category of transition metals. Rather, it helps establish that some transition metals are special and deserve a subcategory and effectively discard the rest of them as less important. That's hardly what I'd want to show in a general-audience PT. I think that there in principle could be a talk of subcategories within categories if we can divide an entire category into subcategories, provided subcategories would be clearly secondary and not displayed in small tables. More than a half of elements in the TM group, however, remains outside of all subgroups, which really puts more spotlight on platinum at the expense of titanium, which I find undesirable.

It appears there is no appetite to say that Sc and Y are rare earth metals and not transition metals, and I find myself glad about that.

To sum it up, I think the proposal will result in a less user-firendly table and put us in more jeopardy because of the category overlap, which is why I suggest we don't implement it.--R8R (talk) 10:58, 20 September 2020 (UTC)[reply]

I fully agree with the well-formulated comment R8R made here.

I add: actually, this would be three levels of categorisation, not two, since we already show metal-metalloid-nonmetal as supercategorisation. Also, I do not see an improvement by introducing Venn-like divisions (like re-using halogen in here). Essence of this (enwiki) categorisation is that it shows categories independent of groups and periods (orthogonality). The fact that some nonmetals are a halogen already is noted by the group name 'halogens'; "halogen nonmetals" readily can be deducted from the PT. That two (only two) categories correspond with groups is incidental. OTOH, other categories, like major catgegory metalloids, actually add new info to the PT. -DePiep (talk) 15:49, 20 September 2020 (UTC)[reply]

Proposed name for group 3

I hereby recommend that the IUPAC adopt a trivial name for the scandium group: the disputogens. You heard it here first. YBG (talk) 22:36, 1 August 2020 (UTC)[reply]

No, that would be too easy. It should be called the "disputogens" only when it means Sc-Y-Lu-Lr. When it means Sc-Y-La-Ac, it should be called the "arguenogens". Perhaps another name should be given to them when all 30 lanthanides and actinides are included (Sc-Y-*-**), such as the "grawlixogens".

(removes tongue from cheek). Double sharp (talk) 04:09, 2 August 2020 (UTC)[reply]

So much for the work of IUPAC's Group 3 project then. Sandbh (talk) 04:33, 2 August 2020 (UTC)[reply]

@Sandbh: I'm quite confident the IUPAC will have no problem separating tongue from cheek as Double sharp and I do. YBG (talk) 05:22, 23 September 2020 (UTC)[reply]

@YBG: I thought it was a disrespectful comment that showed no appreciation of the background to the dispute as well as contributing nothing to the discussion. Sandbh (talk) 06:59, 23 September 2020 (UTC)[reply]

Why do none of the transition metal groups have standardized names?

To give all eighteen groups a common name, may I propose the addition of ten more names?

1: the alkali metals (when excluding hydrogen), 2: the alkaline earth metals, 3: the disputogens, 4: the titanogens, 5: the vanadogens, 6: the chromogens, 7: the manganogens, 8: the ferrogens, 9: the cobaltogens, 10: the nickelogens, 11: the coinage metals, 12: the volatile metals, 13: the icosagens/the trigens, 14: the crystallogens/the tetragens, 15: the pnictogens, 16: the chalcogens, 17: the halogens, 18: the noble gases

We can also extend this to the f block - the lanthanogens, the cerogens, the praseodymogens, the neodymogens, the promethogens, etc.

I know this is WP:OR, but we need better names instead of trying to remember whether nickel is in group 8, group 9, or group 10. ― Дрейгорич / Dreigorich Talk 10:08, 4 August 2020 (UTC)[reply]

@Дрейгорич: They do have standardised names, sort of, in that the IUPAC Red Book provides for them to be called according to the first element in each group, so group 3 is the scandium group.

I’ve seen references to: early transition metals (groups 4 to 7); ferrous metals (Fe, Co, Ni); and of course the platinum group metals.

And there is Group 5 as the acid earth metals. The name is a reference to the acidic nature of the pentoxides of this group. See: Remy H 1956, Treatise on inorganic chemistry, vol. 2, Elsevier, Amsterdam, p. 87

--- Sandbh (talk) 11:41, 4 August 2020 (UTC)[reply]

The acid earth metals. Huh. Well, I know what I'm naming our rock band. ― Дрейгорич / Dreigorich Talk 11:47, 4 August 2020 (UTC)[reply]

@Дрейгорич: You'll be in good company. There was a band called Rare Earth in the 1970s. I see they're still active. Sandbh (talk) 00:35, 7 August 2020 (UTC)[reply]

Pentoxides of V, Nb, and Ta should better be called amphoteric. Pentoxides with weak enough basic character to be safely called acidic rather occur from group 6 onwards. Double sharp (talk) 13:07, 4 August 2020 (UTC)[reply]

Not really; it depends on the context.

Remy writes:

"Fifth sub-group of the periodic system: The acid earths

Although definitely metallic in character in the elementary state, they are decidedly acidic in their normal oxides, the pentoxides. This is true of V, Nb, and Ta at least—and for this reason their pentoxides are also known as the acid earths (i.e., acid-forming metal oxides), or as the earth acids…it appears…the basic character is more strongly developed in Pa than in the first three members of the group, which are not capable of forming simple salts in aqueous solution even with the strongest acids."

Lidin (1996), writing in "Inorganic substances handbook," refers to V₂O₅ as amphoteric with predominating acid properties, and Nb₂O₅ as an acidic oxide. Our article on the latter notes it dissolves in fused alkali. Sanderson (1967), writing in "Inorganic chemistry", rates Ta₂O₅ as amphoteric, favouring acidity.

We can see then that Remy was referring to which side of the basic-acidic line the oxides fell on.

In contrast, Group 4 is a mixed bag: TiO₂ is amphoteric, favouring acidity; and ZrO₂ and HfO₂ are amphoteric, favouring basicity.

I haven't heard of pentoxides of Group 6. From Greenwood & Earnshaw these seem to be intermediate compounds having formulae such as Mo₄O₁₁, Mo₁₇O₄₇, W₁₈O₄₉ and W₂₀O₅₈ (p. 1008). Turning now to the normal oxides of Group 6, MoO₃ is "distinctly amphoteric" (Wiberg 2001, p. 1388) and dissolves in strong acids to form salts which contain the bent molybdanic ion MoO₂²⁺ in hydrated form: [MoO₂(H₂O)₄]²⁺.

Thus, Group 5 is the first group in which the normal oxides favour acidity, hence the term acid earths. --- Sandbh (talk) 01:22, 5 August 2020 (UTC)[reply]

Greenwood and Earnshaw (2nd ed., p. 981): "V₂O₅ is amphoteric. It is slightly soluble in water, giving a pale yellow, acidic solution. It dissolves in acids producing salts of the pale-yellow dioxovanadium(V) ion, [VO₂]⁺, and in alkalis producing colourless solutions which, at high pH, contain the orthovanadate ion, VO₄³⁻."

Greenwood and Earnshaw (2nd ed., p. 982): "Niobium and tantalum also form various oxide phases but they are not so extensive or well characterized as those of vanadium. Their pentoxides are relatively much more stable and difficult to reduce. As they are attacked by conc HF and will dissolved in fused alkali, they may perhaps be described as amphoteric, but inertness is the more obvious characteristic."

Indeed, true that there are no stoichiometric M₂O₅ for group 6, but we can already see acidic properties dominate more from all that polyanion chemistry famous for Mo and W. Greenwood and Earnshaw call +6 oxides of Cr, Mo, and W acidic (p. 1007).

Of course bounds of amphotericity depend on context. There is simply a continuum from more to less acidic properties, different authors may consider a different range of what is sufficient to call an oxide amphoteric. That's why you have to pick one source's classification for consistency. Otherwise the classification is taken out of context. Nb₂O₅ can't possibly be more acidic than MoO₃ with the lower cationic charge by standard general chemistry. Double sharp (talk) 02:37, 5 August 2020 (UTC)[reply]

Some more observations:

• Issa IM and Khalifa H 1954, The amphoteric properties of molybdenum trioxide and its isoelectric point. J. Indian. Chem. Soc. 31, 2. pp. 91-96
• Sisler HH et al. 1959, General chemistry: A systematic approach, Macmillan: "Tungsten trioxide, like its molybdenum analog, is amphoteric, with acidic properties predominating." p. 705
• Songina OA 1970, Rare metals, 3rd ed., Israel Program for Scientific Translations; [available from the U.S. Department of Commerce, Clearinghouse for Federal Scientific and Technical Information, Springfield, Va.: "converted to the anhydride MoO₃ at 115 - 130°C. Both the anhydride and the acid are somewhat amphoteric and readily dissolve in solutions of alkalis." (p. 35).

[Above is an unsigned contribution by Sandbh. Double sharp (talk) 09:17, 5 August 2020 (UTC)][reply]

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Yes, no doubt you can find lots of reliable sources calling MoO₃ amphoteric. But can you find any doing so that also calls Nb₂O₅ acidic like you do when you bring together the different bounds of amphotericity used by Remy and Wiberg? Double sharp (talk) 09:16, 5 August 2020 (UTC)[reply]

The rest of the names

Background

Transition metal group names 3 4 5 6 7 8 9 10 11 12 Scandium group metals Iodide metals1 Acid earth metals Yellow earth metals2 Heptoxide metals3 Red metals4 Weather metals5 Catalytic metals6 Coinage metals Volatile metals Sc Y La Ti Zr Hr V Nb Ta Cr Mo W Mn Tc Re Fe Ru Os Co Rh Ir Ni Pd Pt Cu Ag Au Zn Cd Hg If we can fill out the blanks I'll see I can get the names published in a journal article. Sandbh (talk) 06:52, 5 August 2020 (UTC)[reply] Note 1: Refers to the iodide crystal bar process: "The only metals it has been used to purify on an industrial scale are titanium, zirconium and hafnium, and in fact is still in use today on a much smaller scale for special purity needs." Sandbh (talk) 13:36, 5 August 2020 (UTC)[reply ] Note 2: The background is that lead chromate ) was also referred to as "orange earth". Lead chromate has an orange-yellow colour, so I can see where the reference to orange comes from. The other yellow earths are molybdenum trioxide; and canary yellow tungsten trioxide powder. Sandbh (talk) 00:19, 23 August 2020 (UTC)[reply] Note 3: “The same probably applies to the triads of elements, between the two halves of large periods; they constitute however the transition between these two halves, between the heptavalent metals of the first half of the large periods, whose highest oxides are acidic…”, here Sandbh (talk) 10:17, 5 August 2020 (UTC)[reply] Group 7 as the heptoxide metals refers to the observation that this is the first group with exclusively acidic oxides in their highest oxidation state. (The +6 oxides of group 6, while acidic, all show some amphoteric character.) This is the only group in which binary metal heptoxides are found; each such oxide has a unique crystal structure (Mast 2018, p. 5). Note 4: From the reddish-brown colour of rust; the most prevalent Ru precursor is ruthenium trichloride, a red solid that is poorly defined chemically but versatile synthetically; and the red osmates OsO 4(OH)2− 2 formed upon reaction by OsO4 with a base. Sandbh (talk) 02:28, 7 August 2020 (UTC)[reply ] Note 5: From the use of cobalt chloride as a humidity indicator in weather instruments ; rhodium plating used to "protect other more vulnerable metals against weather exposure as against concentrated acids or acids fumes" (Küpfer 1954, p. 294); and the "rainbow" etymology of iridium. Note 6: From G&E: "They are…readily obtained in finely divided forms which are catalytically very active." (p. 1148). Sandbh (talk) 07:02, 5 August 2020 (UTC)[reply] The new category names do not seem very effective to me. "Scandium metals" seems unnecessary when "scandium group" tells us exactly the same thing and is more standard. "Acid earth metals" for group 4 is in conflict with the citation you got for it where it means group 5 (and ZrO2 and HfO2 are rather on the basic side of amphotericity). "Aerospace metals" seems more relevant to Al than to V, Nb, and Ta. "Yellow metals" is a bit strange for Cr, Mo, and W as none of them are yellow, and Cr compounds are known for many other colours too. "Heptavalent metals" would literally include every metal that manages a +7 oxidation state. "Iron metals" will likely be confusing with the "iron triad". "Catalytic metals" would grab most of the transition metal series, not just Ni, Pd, and Pt. "Volatile metals" would literally include, say, Po. That is my opinion. You may disagree, and if so I will not give more comments on this since this is not WP-related. Double sharp (talk) 11:04, 5 August 2020 (UTC)[reply] @ post transition metal article. I know many TM have catalytic properties. That said, if you asked me about TM catalysts, Pd and Pt would be the first to come to mind. I haven't checked G&E as to why they highlighted group 10 for their very catalytic presence. So there are two groups to go: 6 and 9. Group 9 are the densest group of the TM. Obvious name is heavy metals but that would be confusing. Sandbh (talk) 13:22, 5 August 2020 (UTC)[reply] I don't think "normal" is a good characterisation of oxidation states like Cr(VI) and Mn(VII) that are well-known from high school as strong oxidants. Especially not when maximum oxidation states would include Ag(III), or, even more exotically, Ir(IX). But, since this is for outside Wikipedia, whether you agree with that or not is your choice. "Volatile metals" seems to have a more natural meaning of "a metal that is volatile". Polonium is one such. Using it as a group name requires disambiguating it from the natural meaning. Right, that's it from me. That's because I believe there is no need for special names in the first place. To me: names are for families of chemically related elements. Groups are about valence electrons and orbitals. Families are about the final result, sometimes with a dose of natural occurrence (nobody calls Lr a rare earth metal). These can be vastly different as evidenced by hydrogen in group 1 but outside alkali metals. There is no reason why they must follow especially inhomogeneous and small groups like columns in transition metals. In fact the famous family of rare earths in this region includes group 3 but expands well beyond it. So, I don't think I can give feedback about how best to do something that I don't believe is needed. You may disagree, in which case I wish you the best at it. Double sharp (talk) 13:55, 5 August 2020 (UTC)[reply] ​G&E (p. 27) refer to the highest normal oxide of each element. Clearly, these are the heptoxides M2O7 for the group 7 metals. I've changed their name to the heptoxide metals. This is for WP, as an encyclopaedia, which we always try to improve. If something we think would be an improvement is not in the literature, we can seek to get it into the literature. Example: the metalloid article was unstable due to disagreement about which elements were metalloids. I wrote an article on this which was published in JChemEd. The result? Our metalloid article is now stable and attained FA status. I've withdrawn the name "Iron group metals" for the reason you gave i.e. that it more often refers to the ferromagnetic metals Fe Co and Ni. "Volatile metals" is in the literature. The “volatile” refers to their low melting points compared to neighbouring metals in this part of the periodic table. Indeed, there is an abrupt and significant reduction in physical metallic character from group 11 to group 12 (Sorensen 1991, p. 3). Special names, didactically speaking, give folks something memorable to hang their hats on. That is why they are useful. --- Sandbh (talk) 07:31, 6 August 2020 (UTC)[reply] @Sandbh: G&E quoting the "highest normal oxide" is not a statement about highest oxidation states always being normal. "Normal oxides" means a real oxide with O2− as the counteranion, not peroxide or superoxide. So, K2O, for instance, rather than K2O2 or KO2. Just getting something you think is an improvement into the literature does not mean that you can get it onto WP. If no one but you gives something in the literature, it's simply WP:SELFCITE . It is increasingly my opinion that our colouring is itself not something that we should have done in the first place. Different sources show many different colourings, the colourings give the wrong idea that an element belongs to one and only one category and that they are exhaustive, and picking some sources' view as opposed to others and deciding which is better ourselves is a matter of WP:SYNTH . We can't make arguments on Wikipedia unless you can find them in the literature. It would have been better, in my opinion, to only colour blocks as I do on my userpage, as those are at least generally referred to as a basis even if few actually seem to define them. That will not necessitate any funny business with helium: it can still be an s block element above Ne. The metal-to-nonmetal trend can be mentioned, most of the text present can still be there as bald statements, but we cannot make the decision as to which to believe and colour ourselves with this much variation. And yes, by the way: all those arguments I have been stating in favour of Lu are fair game. They are in the literature, I did not make them up myself, so we can quote them. Double sharp (talk) 07:44, 6 August 2020 (UTC)[reply] @Double sharp: Here's the quote by G&E: "…O elicited an increasing valence in the highest normal oxide of each element and this was directly related to group number, i.e. M2O, MO, M2O3,…M2O7." (p. 27) I'll thank you for the courtesy of not treating me as if I were a newbie. I'm well familiar with WP:IAR we have always sought to improve WP as an encyclopedia. The colouring of our table is what attracted me to WP in the first place, many years ago. I suspect many other folk find it engaging. The most popular PT on the web is based on our colour-category approach. Our colouring scheme inspired my 2020 peer-reviewed article in Foundations of Chemistry, "Organising the metals and nonmetals" (2,200+ accesses to date). Among other things, the article lists several didactic advantages, including the following: "The accompanying periodic table (see the Electronic supplementary material) incorporates elements of learning theory with its use of annotations to facilitate perceptual grouping; colour to differentiate ideas and direct attention to key topics; and “natural" classes or clusters to organise information and help with content processing (Richey et al. 2010)." We do not engage in the practice of, "picking some sources' view as opposed to others and deciding which is better ourselves". Rather, we strive to show what appears to be the most representative categorisation according to the literature. When a category is finely balanced, as in the roughly 50:50 treatment of group 12, we discussed it and coloured the group as PTM. When it came to astatine, R8R suggested colouring it as a metalloid, which we all supported (= no dissent). I don't understand the basis for your statement that, "the colourings give the wrong idea that an element belongs to one and only one category and that they are exhaustive". Our PT article makes it clear this is not the case. Ditto my JChemEd article. Chemists need not lose sleep over such matters. As Nelson (2011), a chemist, said: "…care needs to be taken to remember that…[this classification scheme] is only an approximation, and can only be used as a rough guide to the properties of the elements. Provided that this is done, however, it constitutes a very useful classification, and although purists often despise it because of its approximate nature, the fact is that practising chemists make a great deal of use of it, if only subconsciously, in thinking of the chemistry of different elements." It seems to me that, with occasional bouts of tethchiness, we strive (as best we can) to take account of the literature. Where the literature is shabby, we do our best to be representative, and discuss and acknowledge the shabbiness in the applicable article. Where one of us feels prompted to address the gap, and put in the sizeable effort to do so, we seek to get published in the literature. There'll be many more arguments in support of La in group 3, when my peer-reviewed article on the location and composition of group 3 soon appears in Foundations of Chemistry (editor Eric Scerri). Sandbh (talk) 13:29, 6 August 2020 (UTC)[reply]

@Дрейгорич: That was a great question of yours. I subsequently got an e-mail from a chemistry professor saying "I love this…weather metals, especially!"

No prob. I just had it as a random question in my head. It started with the "disputogens" and I wondered... if we're doing one group of the 18, why not all of them? ― Дрейгорич / Dreigorich Talk 03:27, 9 August 2020 (UTC)[reply]

Colleagues, here's the outcome, which I've asked Dr Mark Leach to host at the Internet database of periodic tables. Happy reading. I intend to have the names published in a peer-reviewed journal. Sandbh (talk) 02:58, 9 August 2020 (UTC)[reply]

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Representative and transition element (RATE) group names

A colleague asked why none of the transition (technicolour) metal groups have standardised names. "We need better names instead of trying to remember whether nickel is in group 8, group 9, or group 10." They do have standardised names, sort of, in that the IUPAC Red Book (Connelly et al. 2005) provides for them to be called according to the first element in each group, so group 3 is the scandium group. But that is a rather dull practice and I have enough trouble recalling the order of the 3d metals let alone the members of e.g. the cobalt group. Didactically speaking, special names give folks something memorable to hang their hats on. Here is listing of group names, including for the transition elements. Looking at the names now I recall how uninspiring my introduction was to the "no group name" transition metals, many years ago. Group names 1 Li to Fr Hydrogen and the alkali metals 2 Be to Ra Alkaline earth metals 3 Sc Y La Scandium group metals ------------------------------------- 4 Ti Zr Hf Iodide metals 5 V Nb Ta Acid earth metals 6 Cr Mo W Chromatic earth metals 7 Mn Tc Re Heptoxide metals 8 Fe Ru Os Rubiferous metals 9 Co Rh Ir Weather metals 10 Ni Pd Pt Catalytic metals 11 Cu Ag Au Coinage metals 12 Zn Cd Hg Volatile metals 13 B to Tl Icosagens 14 C to Pb Crystallogens ----------------------------- 15 N to Bi Pnictogens 16 O to Po Chalcogens 17 F to At Halogens 18 He to Rn Noble gases Of the above names, only those for groups 1–3 and 15–18 are mentioned in the IUPAC Red Book on the nomenclature of inorganic chemistry. 1 — Alkali metals: Rarely, hydrogen and the alkali metals. Self explanatory, but for hydrogen. Hydrogen is nearly always placed above lithium. Otherwise it is placed floating by itself (sometimes with helium) in the middle of and above the periodic table; above boron, or carbon or straddling boron and carbon; or above fluorine. The position of hydrogen in group 1 is quite well settled. It does not matter that hydrogen is a nonmetal and a gas, in the same way that it does not matter that oxygen in group 16 is a nonmetal and a gas whereas polonium, at the other end of group 16, is a metal and a solid. Similarities of hydrogen with lithium: Both have significant covalent chemistry Lithium, like hydrogen, when bound to highly electronegative atoms such as nitrogen, oxygen, or fluorine, is capable of forming electrostatic bonds with other nearby highly electronegative atoms Their spectra are similar. Similarities with the alkali metals: In chemical reactions, hydrogen and the alkali metals usually lose their single valence electrons; all usually have a valence of +1 Both form similar compounds e.g. hydrogen chloride (HCl) and alkali metal chlorides (XCl) Like hydrogen, most of the alkali metals can form compounds with a charge or oxidation state of –1 Hydrogen can stand in for alkali metals in typical alkali metal structures; see: Hydrogen adopts alkali metal position (Wilson 2013) Hydrogen is capable of forming alloy-like hydrides, featuring metallic bonding, with some transition metals. The anomalous properties of hydrogen can be explained by its unique electron configuration, in that it has no underlying core of electrons. 2 — Alkaline earth metals: Historically, beryllium and magnesium were not counted as alkaline earths (Parish 1977). Beryllium is amphoteric rather than alkaline; magnesium was first isolated, in an impure form, by heating the oxide with charcoal thereby showing it was not an intractable "earth". 3 — Scandium group metals: Scandium, yttrium, and lanthanum were all discovered in mineral samples from Sweden. There is a minor controversy as to the composition of the group. The third and fourth members are either lanthanum and actinium, or lutetium and lawrencium. Most tables show the former although there has been some increasing interest in the latter. There is an IUPAC project considering the matter, here. 4 — Iodide metals: "Van Arkel and de Boer developed the iodide decomposition process [in 1924] to make a pure, ductile metal [Zr] in Eindhoven, Holland. The "iodide crystal bar" process continues to be used today as method of purifying Ti, Zr, and Hf, even thought it is slow and expensive." (Schweitzer 2006, p. 571) 5 — Acid earths: "Although definitely metallic in character in the elementary state, they are decidedly acidic in their normal oxides, the pentoxides. This is true of V, Nb, and Ta at least—and for this reason their pentoxides are also known as the acid earths (i.e., acid-forming metal oxides), or as the earth acids…it appears…the basic character is more strongly developed in Pa than in the first three members of the group, which are not capable of forming simple salts in aqueous solution even with the strongest acids." (Remy 1956, p. 87) 6 — Chromatic earth metals: Etymology: < French chrome, < Greek χρῶμα colour. ^ Chromic acid, of which Cr(III) oxide is the anhydride, has an orange-red appearance † Cr(VI) oxide dissolves in small amounts of water to give yellow-red to red polychromic acids while in larger amounts of water it yield yellow chromic acid solution ‡ Reduction reactions of MoO3 in acid can yield dark red Mo2+4; green-yellow Mo+3; and yellow-orange Mo2O4+2 § On heating, Mo or W metal is transformed progressively into violet to blue-black metallic conducting phases MO3–2 II Tungstite WO3·H2O is formed by the weathering of tungsten containing minerals; it crystallizes in translucent yellow to yellow green masses ¶ Mild reduction in acid medium of WO3·2H2O gives intensely coloured tungsten blue, this being a general term applied to complex mixtures of W(VI) and W(V) oxides and hydroxides # "Thermochromism is the property of substances to change colour due to a change in temperature and WO3 is an attractive example for this property. On cooling the oxide by liquid nitrogen down to –196°C, a sudden change occurs from yellow to white, which then alters to a bluish-white colour between –50 and –27°C. At room temperature it becomes pale lemon-yellow again. On further heating to 200 – 300°C, WO3 becomes dark yellow, changing to a deep orange colour at 400 to 500°C” (Weil & Schubert 2013). ^ Chromic acid, of which Cr(III) oxide is the anhydride, has an orange-red appearance. That chromium is the first of the chromatic earths is apt. Weil M & Schubert W-D 2013, "The beautiful colours of tungsten oxides", Tungsten Newsletter, June, ITAA, https://www.itia.info/assets/files/newsletters/Newsletter_2013_06.pdf, viewed Aug 5th, 2020 7 — Heptoxide metals: "The same probably applies to the triads of elements, between the two halves of large periods; they constitute however the transition between these two halves, between the heptavalent metals of the first half of the large periods, whose highest oxides are acidic…" (Walter 1909, p. 269) Group 7 as the heptoxide metals refers to the observation that this is the first group with exclusively acidic oxides in their highest oxidation state. (The +6 oxides of group 6, while acidic, all show some amphoteric character.) Further, this is the only group in which binary metal heptoxides are found, each such oxide having a unique crystal structure (Mast 2018, p. 5). 8 — Rubiferous metals: (classical Latin rubēre to be red; -fer producing); from the reddish-brown colour of rust; the most prevalent ruthenium precursor being ruthenium trichloride, a red solid that is poorly defined chemically but versatile synthetically; and the red osmates OsO 4(OH)2− 2 formed upon reaction by osmium tetroxide with a base. Iron causes our blood to be red. Iron is the most important structural metal. More than $10 billion is lost each year to corrosion in the US alone. Much of this corrosion is the rusting of iron and steel. The etymology of the word 'rust' has its origins in the Proto-Germanic word rusta, which translates to "redness". That iron is the first of the Group 8 rubiferous metals is a rich juxtaposition. 9 — Weather metals: From the use of cobalt chloride as a humidity indicator in weather instruments; rhodium plating used to "protect other more vulnerable metals against weather exposure as well as against concentrated acids or acids fumes" (Küpfer 1954, p. 294); and the "rainbow" etymology of iridium. 10 — Catalytic metals: "They are…readily obtained in finely divided forms which are catalytically very active." (Greenwood & Earnshaw 2002, p. 1148). Of course, many transition metals have catalytic properties. That said, if you asked me about transition metal catalysts, palladium and platinum would be the first to come to mind. And, per Greenwood and Earnshaw, group 10 appear to be particularly catalytic. 11 — Coinage metals: Historically, most coinage metals (or alloys) are made from copper, silver or gold, the copper usually being augmented with tin and often other metals to form bronze. Roe and Roe (1992) noted 24 metals had been used in coins of the world. Curiously, chromium and manganese were not mentioned by them, even though both elements had been used in common circulation coins (Canada wartime V nickels and US wartime Jefferson nickels, respectively) long before the time of their article's publication. 12 — Volatile metals: The "volatile" refers to their low melting points compared to neighbouring metals in this part of the periodic table. Thus, there is an abrupt and significant reduction in physical metallic character going from group 11 to group 12 (Sorensen 1991). 13 — Icosagens: A reference to the frequency of icosahedral structures seen in this group (Greenwood & Earnshaw 2002, p. 227). 14 — Crystallogens: After the capacity of carbon, silicon, germanium, and grey tin to adopt regular covalent network structures. Rarely adamantogens (Jensen n.d.) or merylides (Fernelius 1971; Fernelius et al. 1983). The origin of merylides is obscure, perhaps mer-, part; -yl, ancient Greek ὕλη (húlē, “wood, material”)" and -ide, one belonging to a specific natural group (Websters 2002), thus charcoal, coal, carbon. On this suggestion, Fernelius et al. (1971) commented that, "It has been proposed, but has not yet become widely used. Let us hope that it never does. New terms should be derived from familiar roots, not unknown ones." 15 — Pnictogens: from pnigmos, suffocation; a reference to the life-extinguishing capacity of nitrogen. 16 — Chalcogens: The word "chalcogen" is derived from a combination of the Greek word khalkόs (χαλκός) principally meaning copper (the term was also used for bronze/brass, any metal in the poetic sense, ore or coin), and the Latinised Greek word genēs, meaning born or produced. The connection is to the ores that copper forms with sulfur, and to a lesser extent oxygen. 17 — Halogen: The name means "salt-producing". When halogens react with metals, they produce a wide range of salts, including calcium fluoride, sodium chloride (common table salt), silver bromide and potassium iodide. 18 — Noble gases: Rarely aerogens. Since oganesson is unlikely to be a gas and and is expected to be relatively reactive, perhaps group 18 may need to be renamed as the helium group. † The yellow aspect of the group 6 metals spills over into their neighbours, the heptoxide metals, and iron. Thus the heptoxides of technetium and rhenium are yellow. For manganese, on the other hand, yellow is a rare colour. There are a few references to manganese yellow glassware however the colour arises from the presence of iron rather than manganese per se. Here manganese, as green manganese oxide, oxidises iron from its ferrous (+2) state to its ferric (+3) state yielding yellow iron(III) oxyhydroxide (Corning 2011). References Connelly NG, Damhus T, Hartshorn RM and Hutton AT 2005, Nomenclature of inorganic chemistry: IUPAC recommendations 2005, International Union of Pure and Applied Chemistry, RSC Publishing, Cambridge Corning Museum of Glass 2011, Decolorizers (Manganese dioxide) Fernelius WC, Loening K & Adams RM 1971, 'Names of groups and elements', Journal of Chemical Education, vol. 48, no. 11, p. 730; Fernelius WC 1983, 'Group names', Journal of Chemical Education, vol. 60, no. 2, p. 140. Greenwood NN & Earnshaw A 2002, Chemistry of the elements, 2nd ed., Butterworth-Heinemann, Oxford Grochala W 2020, Watch the colors: or about qualitative thinking in chemistry, open access Jensen WB n.d., The periodic law and table, unpublished article for Encyclopedia Britannica, p. 10 Küpfer YJ 1954, Rhodium uses in plating, Microtecnic, Agifa S.A. Mast, DS 2018, Crystallographic exploration of fundamental technetium species at nonambient conditions, UNLV Theses, Dissertations, Professional Papers, and Capstones 3368 Parish RV 1977, The metallic elements, Longman, New York Remy H 1956, Treatise on inorganic chemistry, vol. 2, Elsevier, Amsterdam Roe J and Roe M 1992, "World's coinage uses 24 chemical elements", World Coin News, Feb. 17, pp. 24–25; Mar. 2, pp. 18–19. Schweitzer PA 2006, Fundamentals of metallic corrosion: Atmospheric and media corrosion of metals, 2nd ed. CRC Press, Boca Raton, p. 571 Sorensen EMB 1991, Metal poisoning in fish, CRC Press, Boca Raton, Florida, p. 3 Walter CW (ed) 1909, Ion, vol. 1: Zeitschrift für Electronik, Atomistik, Ionologie, Radioactivität und Raumchemie, London Websters 2002, A dictionary of prefixes, suffixes, and combining forms Wilson P 2013, Hydrogen adopts alkali metal position, Chemistry World --- Sandbh (talk) 02:58, 9 August 2020 (UTC)[reply]

Some arguing

I have decided to remove what used to be here as more heat than light is generated. Even though I still disagree with almost everything Sandbh says about chemistry and his interpretations of the sources, I feel that I went too far again, and I also feel that if something makes me unnecessarily unhappy, I should just stop doing it. So I leave the project instead. Double sharp (talk) 10:14, 7 August 2020 (UTC)[reply]

This is very sad news. [2] -DePiep (talk) 10:42, 7 August 2020 (UTC)[reply]

@DePiep: My apologies. But I will soon just lack the time due to RL commitments. And even if that was not a consideration, I feel that the general understanding of periodicity is so intertwined with all element articles that I simply will not be able to work here as long as this dispute cannot be resolved. Neither me nor Sandbh will accept the other party's view of the situation and reliable sources, and it's best for my emotional state and real life to just let go and leave. Even if I still think I'm right, why fight? It will make me unhappy.

I have drafted a second

RFC on the group 3 dispute. I may still post it for the others who have talked about this, because after over seven months of arguing, they deserve an RFC. But I will not comment on whatever Sandbh posts there. Double sharp (talk) 10:51, 7 August 2020 (UTC)[reply

]

I understand, incl the wellbeing point. -DePiep (talk) 11:23, 7 August 2020 (UTC)[reply]

@DePiep: Thank you. ^_^ Double sharp (talk) 12:11, 7 August 2020 (UTC)[reply]

Since the RL time and situation-inflaming issues apply even to starting an RFC: I will not start one. Goodbye. Double sharp (talk) 14:20, 7 August 2020 (UTC)[reply]

@Double sharp: As I see it, there is no dispute. I have a view. You have a different view. That happens all day every day all over the world. This doesn't constitute a dispute, unless one or the other of us wants to treat it as such. I've made various proposals within our project over the years. Some got up some didn't. So it goes. I get past the failures, and incorporate what I learnt into my next contribution or project. I'll check with you after a while and see how you're going. Sandbh (talk) 03:27, 8 August 2020 (UTC)[reply]

@Sandbh: Well, that's good to hear. Now I focus on my RL work. ;) Double sharp (talk) 04:06, 8 August 2020 (UTC)[reply]

@Double sharp: Righto. When you feel like a breather from RL work, or some pop corn for the brain ^_^, feel free to drop by. I'll miss your insights and perspectives, for as long as you decide to un-participate. Sandbh (talk) 05:28, 8 August 2020 (UTC)[reply]

@Sandbh: You may still find them at the usual place as long as I'm not around here. I hope, it is not objectionable as a presentation to you. Take it as an opinion piece. ^_^ Right, no hard feelings left on either side I hope. Double sharp (talk) 05:38, 8 August 2020 (UTC)[reply]

@Double sharp: Hard feelings don't work for me. They're like an anchor I have to drag around. So yes, absolutely none. Some other people like to drag anchors around so they can have pity parties e.g. or can blame their woes on what a short deal they've got at out life. Not me. Not you, I hope and trust. It's not question of either RL or WP:ELEMENTS. You can have and enjoy both if you choose to do so. "Tears or cantankerous arguments" aren't required. Sandbh (talk) 06:02, 8 August 2020 (UTC)[reply]

P.S. you can probably expect me back when IUPAC finally decides on a group 3 constitution. So you may pencil that in. Reason being that that would have to resolve

the difference in philosophy that explains why such issues tend to blow up. See you then! XD Double sharp (talk) 21:16, 15 September 2020 (UTC)[reply

]

Double sharp: I feel no particular philosophy is intrinsically "better" than any other. They all show differing manifestations of periodicity which, as we know, is only ever approximate in the first place. More important is to explain the context for the arrangement of the particular periodic system at hand. It occurs to me that this principle applies to e.g. the location of H and He, and the location and composition of group 3. As you express it, deducing "the properties of the objects being classified from something very basic" and arranging a periodic table on this basis or, say, on wave mechanical grounds, will show some aspects of periodicity and not others seen in different arrangements.

Only an n-dimensional entity would be able to arrange the elements in such a way as to show every manifestation of periodicity. Here, shall we say n = 6^{6^6}. Since we are stuck with the three or four dimensions that we can sense, we have to satisfy ourselves with one slice of this n-dimensional space at a time.

In this context, I doubt IUPAC will make a ruling. I expect they will come up with something like this:

Draft IUPAC Red Book guidance

ELEMENTS IN THE PERIODIC TABLE

The periodic table on the insider cover is the form agreed and used within the IUPAC, rather than being IUPAC recommended or approved. In this instance, the lanthanoids are shown as a 15-element wide series in light of their chemical similarities.

Different forms of the periodic table may be more or less appropriate in particular contexts. For example, a 14-element wide lanthanoid series may be more appropriate to better bring out the concept of an f-block. Such a series could start with, for example, lanthanum or cerium depending on the context.

IUPAC does not recommend or approve any particular format of periodic table or system, nor does it mandate the composition of Groups.

I expect they will still publish the report of the Group 3 project as a fine and informative research paper.

--- Sandbh (talk) 01:05, 16 September 2020 (UTC)[reply]

@Sandbh: Well, let's just say we disagree about this. The difference in philosophy about what periodicity really is means neither of us is likely to convince each other, so let's not try till the report comes out. But hopefully you found my linked essay somewhat interesting and hopefully it does not misrepresent you. ^_^ So, I guess you will be rooting for the above outcome, and I will be rooting for an outcome that recommends Lu under Y. I will await the report with interest – incidentally, if you have any indication about when it is likely to come out, I would be interested to hear it – and then make up my own mind about it after reading it. Double sharp (talk) 07:22, 16 September 2020 (UTC)[reply]

Double sharp: I won't mind which way they go. After the project completes its report it will go to someone or some committee for approval to publish as an IUPAC report/recommendation suitable for release. This is not guaranteed. Then it would be released for comments by the chemistry community, among others, for (say) six months. Then the comments get considered by IUPAC to see if the project report's recommendation should receive IUPAC endorsement. This is not guaranteed.

I'll ask Eric where things are up to once my article appears online. That would've happened by now but for issues I've experienced with the outsourced (= no accountability; no QA; no coordination) proof production company, and have repeatedly complained about to a cast of a dozen+ people. Finally I rec'd the 6th[!] proof (43 pp) today, and it has only three errors in it, subject to a final read tomorrow. Heavens be, what a saga. Six months to write. I uploaded the MS on 6 Jul. Ten and a half working weeks have passed and the end may be in sight. And the standard response from the proof production company, when you load your MS the first time, is that you only get ONE proof! I've knocked them back five times. I hope I've set a record. There will be a nice old fashioned snail mail formal letter of complaint going to the CEO of the publishing company once this is over.

@Sandbh: Interesting. We'll see what happens, and looking forward to hearing where things are at.

Well, good luck with your publication, and sorry to hear about these problems. ^_^ Double sharp (talk) 10:09, 16 September 2020 (UTC)[reply]

The periodic table: Past, present, and future

Now out.

By Geoff Rayner-Canham

https://www.worldscientific.com/worldscibooks/10.1142/11775

Split d-block

I stumbled upon a transcript of a 1981 Bakerian lecture, here, by RJP Williams who, with CSG Phillips, wrote a remarkable advanced two volume set on Inorganic chemistry, in 1965. From a 1967 book review: "We have inorganic chemistry presented here as the difficult and complex subject it is. The approach is thoroughly adult, and the level is probably more advanced than our students have came to expect."

Williams writes (pp. 362-363):

2. THE CHEMICAL CLASSIFICATION OF ELEMENTS

"The classification of elements in the Periodic Table is now known to be a reflection of restrictions imposed by quantization of energy states of electrons in atoms. However, without recourse to other than empiricism in the study of chemistry the same classification had been observed for over 100 years. In fact it has long been a standard educational practice to separate elements into Groups IA, IIA, and IIIA; transition metals; Groups IB, IIB and IIIB; and the non-metals of Groups IVB to VIIB of the Periodic Table to simplify discussion of their chemistry. Although the distinctive properties in aqueous solution of each of the four classes does not provide sharp divisions it is very useful to treat separately three types of metal: Groups IA, IIA and IIIA metals are associated with equilibrium ionic-model chemistry; transition metals with one-electron redox chemistry and, across each such series, increasingly covalent chemistry concommitant with increasing Lewis-acid strengths of ions, usually at equilibrium with their surroundings; and Groups (IB), IIB and IIIB metal ions with a compromise ion chemistry involving strong Lewis-acid properties while maintaining fast equilibration but little redox activity…Finally, there is the further chemistry of non-metals…"

The upshot is that, according to Phillips, and in the specific context of simple chemistry, a split d block is very useful. --- Sandbh (talk) 03:28, 18 August 2020 (UTC)[reply]

The remarkable chemistry of the pre-halogen nonmetals

I have a completed manuscript (5,000 words) if anybody would like to review it pre-publication. --- Sandbh (talk) 00:59, 21 August 2020 (UTC)[reply]

A partially disordered periodic table

Extended content

Here’s a 15-column table which is a hybrid of a Mendeleev 8-column table and an 18-column standard table. The key relocations are the p-block nonmetals to the far left; and the coinage and post-transition metals under their s and early d block counterparts Taking a leaf out of DIM’s playbook, I ignored atomic number order when this seemed appropriate. It’s refreshing to see the traditional horizontal gaps between blocks disappear. DIM didn’t like these. Since Dias (2004) reckoned a periodic table is a partially ordered set forming a two-dimensional array, I believe I now have a partially ordered table that is partially disordered twice over. The table has some curious relationships. Equally, some relationships seen in the standard form are absent. The Group 2, 3, and aluminium dilemmas disappear. This confirms my impression that such dilemmas have no intrinsic meaning. Rather, their appearance or non-appearance is context dependent. The rest of my explanatory notes and observations follow. Groups 1 to 4 have either a C or F suffix where C (nonmetal) is after the importance of carbon to our existence; and F (metal) is for the importance of iron to civilisation. Groups 1C and 1F present the greatest contrast in nonmetallic and metallic behaviour. Coactive nonmetals: They are capable of forming septenary heterogeneous compounds such as C20H26N4O10PSSe. Group 2C: Helium is shaded as a noble gas. "Heliox" is a breathing gas mixture of helium and oxygen used in saturation diving, and as a medical treatment for patients with difficulty breathing. Group 3C: Boron over nitrogen looks odd. Yet one boron atom and one nitrogen atom have the same number of electrons between them as two adjacent carbon atoms. The combination of nitrogen and boron has some unusual features that are hard to match in any other pair of elements (Niedenzu & Dawson 1965). Boron and phosphorus form a range of ring and cage compounds having novel structural and electronic properties (Paine et al. 2005). Metalloids: I treat them here as nonmetals given their chemistry is predominately that of chemically weak nonmetals. Metals: The labels electropositive; transition; and electronegative are adapted from Kornilov (2008). Group 1F: Monovalent thallium salts resemble those of silver and the alkali metals. An alloy of cesium (73.71%), potassium (22.14%) and sodium (4.14%) has a melting point of −78.2 °C or −108.76 °F (Oshe 1985). Silver, copper, and gold, as well as being the coinage metals, are borderline post-transition metals. Group 2F: Beryllium and magnesium are not in fact alkaline earths. Beryllium is amphoteric rather than alkaline; magnesium was isolated in impure form from its oxides, unlike the true alkaline earths. The old ambiguity over whether beryllium and magnesium should go over calcium or zinc has gone. Nobelium is here since +2 is its preferred oxidation state, unlike other actinoids. Group 3F: Aluminium is here in light of its similarity to scandium (Habishi 2010). InGaAsP is a semiconducting alloy of gallium arsenide and indium phosphide, used in lasers and photonics. There is no Group 3 "issue" since lanthanum, actinium, lutetium and lawrencium are in the same family. Gold and aluminium form an interesting set of intermetallic compounds known as Au5Al2 (white plague) and AuAl2 (purple plague). Blue gold is an alloy of gold and either gallium or indium. Lanthanoids: The oxidation state analogies with the transition metals stop after praseodymium. That is why the rest of lanthanoids are footnoted in dash-dot boxes. Actinoids: The resemblance to their transition metal analogues falters after uranium, and peters out after plutonium. Group 4F: It’s funny to see titanium—the lightweight super-metal—in the same group as lead, the traditional "heavy" metal. This is the first group impacted by the lanthanoid contraction (cerium through lutetium) which results in the atomic radius of hafnium being almost the same as that of zirconium. Hence "the twins". The chemistry of titanium is significantly different from that of zirconium and hafnium (Fernelius 1982). Lead zirconate titanate Pb[ZrxTi1−x]O3 (0 ≤ x ≤ 1) is one of the most commonly used piezo ceramics. Group 5: Bismuth vanadate BiVO4 is a bright yellow solid widely used as a visible light photo-catalyst and dye. Steel friends: The name is reference to their use in steel alloys. They have isoelectronic soluble oxidizing tetroxoanions, plus a stable +3 oxidation state. (Rayner-Canham 2020). Ferromagnetic metals: The horizontal similarities among this triad of elements (as is the case among the PGM hexad) are greater than anywhere in the periodic table except among the lanthanides (Lee 1996). The +2 aqueous ion is a major component of their simple chemistry (Rayner-Canham 2020). Group 8: "Rubiferous metals" (classical Latin rubēre to be red; -fer producing) is from the reddish-brown colour of rust; the most prevalent ruthenium precursor being ruthenium trichloride, a red solid that is poorly defined chemically but versatile synthetically; and the red osmates OsO 4(OH)2− 2 formed upon reaction by osmium tetroxide with a base. Group 9: "Weather metals" comes from the use of cobalt chloride as a humidity indicator in weather instruments; rhodium plating used to "protect other more vulnerable metals against weather exposure as well as against concentrated acids or acids fumes" (Küpfer 1954); and the "rainbow" etymology of iridium. Group 10: "Catalytic metals" is after a passage in Greenwood and Earnshaw, "They are…readily obtained in finely divided forms which are catalytically very active." (2002). Of course, many transition metals have catalytic properties. That said, if you asked me about transition metal catalysts, palladium and platinum would be the first to come to mind. And group 10 appear to be particularly catalytic. References Dias JR 2004, "The periodic table set as a unifying concept in going from benzenoid hydrocarbons to fullerene carbons", in DH Rouvray & RB King (eds.), The periodic table: into the 21st century, Institute of Physics Publishing, Philadelphia, pp. 371–396 (375) Fernelius WC 1982, "Hafnium," J. Chem. Educ. vol. 59, no. 3, p. 242 Greenwood NN & Earnshaw A 2002, Chemistry of the elements, 2nd ed., Butterworth-Heinemann, Oxford, p. 1148 Habashi F 2010, "Metals: typical and less typical, transition and inner transition", Foundations of Chemistry, vol. 12, pp. 31–39 Lee JD 1996, Concise inorganic chemistry, 5th ed., Blackwell Science, Oxford, p. 753 Kornilov II 1965, "Recent developments in metal chemistry", Russian Chemical Reviews, vol. 34, no. 1, p. 33 Küpfer YJ 1954, "Rhodium uses in plating", Microtecnic, Agifa S.A., p. 294 Niedenzu K & Dawson JW 1965, Boron-nitrogen compounds, Springer, Berlin, preface Oshe RW (ed.) 1985, Handbook of thermodynamic and transport properties of alkali metals, Blackwell Scientific, Oxford, p. 987 Paine et al. 2005, "Recent developments in boron-phosphorus ring and cage chemistry", in Modern aspects of main group chemistry, M Lattman et al. (eds.), ACS Symposium Series, American Chemical Society, Washington DC, p. 163 Rayner-Canham G 2020, The periodic table: Past, present, and future, World Scientific, Singapore --- Sandbh (talk) 12:18, 27 August 2020 (UTC)[reply] I would readily describe this PT as not being "groupic", but I would not say the same about "our" enwiki PT. (See special:diff/973773980) YBG (talk) 05:40, 1 September 2020 (UTC)[reply] Nice. If scientifically relevant, do propose & argue for Alternative periodic tables. (I'd say: if structurally new, then add. If editorial variant - forget it). -DePiep (talk) 20:42, 6 September 2020 (UTC)[reply ]

Lanthanoid vs Lanthanide

The 1985 “Red Book” (p. 45) indicates that the following collective names for groups of atoms are IUPAC-approved: actinoids or actinides, lanthanoids or lanthanides. The note that accompanied that statement explained that although actinoid means “like actinium” and so should not include actinium, actinium has become common usage. Similarly, lanthanoid. The ending “-ide” normally indicates a negatives ion, and therefore “lanthanoid” and “actinoid” are preferred to “lanthanide” and “actinide.” However, owing to wide current use, “lanthanide” and “actinide” are still allowed. http://publications.iupac.org/ci/2004/2601/2_holden.html

Does anybody has a good overview, when exactly

IUPAC

moved from lanthanide to lanthanoid, while still allowing the name lanthanide for continuity? Was it the 1985 version of the "Nomenclature of Inorganic Chemistry" or was it already done earlier?

The 2005 Version of the Red Book says on page 52: "Although lanthanoid means ‘like lanthanum’ and so should not include lanthanum, lanthanum has become included by common usage. Similarly, actinoid. The ending ‘ide’ normally indicates a negative ion, and therefore lanthanoid and actinoid are preferred to lanthanide and actinide." On page 311 it says that lanthanide is the anion of lanthanum. --Gunnar (talk) 22:25, 5 September 2020 (UTC)[reply]

See the discussion

WP:common usage. Polyamorph (talk) 15:14, 8 September 2020 (UTC)[reply

]

Thank you for the link to the discussion from 2010, that was interesting. As things tend to change, if is worth while to check if the decision taken years ago is still valid. I don't say that we must revert old decisions, I only say it must not be forbidden to re-evaluate decisions of past. In standardisation we call this stability date: for a given time, a decision (set of requirements) is not touched. After the stability date, the standard is either re-confirmed, reviewed or withdrawn. --Gunnar (talk) 17:12, 8 September 2020 (UTC)[reply]

Given that lanthanide remains in the most

common use (try a google scholar search of the two terms to see for yourself) I don't see any need to re-evaluate the previous consensus regarding article naming at this time. However, article content discussing the naming convention might require development/updating if new sources are available. Polyamorph (talk) 18:04, 8 September 2020 (UTC)[reply

]

The original post here in this thread was: "Does anybody has a good overview, when exactly

IUPAC moved from lanthanide to lanthanoid"? The detailed discussion weather to say "lanthanide, also called lanthanoid" or "lanthanoid, also called lanthanide" should take place at the relevant article's talk page. And I am happy to review a decision 10 years old, maybe some arguments are seen differently today. I personally are a tiny bit surprised that in the field of science (and chemistry is not a social science, but a rather exact one with clear rules), that the normative power of the professional association that defines the naming conventions has not been respected. --Gunnar (talk) 14:31, 10 September 2020 (UTC)[reply

]

The discussion can take place wherever the participants choose to do so. Chemistry is not an exact science. It is replete with idiosyncrasies, fuzzy rules, and ignored IUPAC recommendations. Sandbh (talk) 13:41, 17 September 2020 (UTC)[reply]

Lining up the periodic table

Extended content

For reading interest.

48-crash line: Named after the dramatic reduction in physical metallic character after group 11, Cd being Z = 48. Group 12 show few transition metal attributes and behave predominantly like post-transition metals.

Big bang line: H makes up about 73% of the visible universe.

Corrosive line: O, F, Cl = most corrosive nonmetals.

d-fault line: Group 3 show little d-block behaviour; group 4 is the first in which characteristic d-block behaviour occurs.

Deming line: Demarcates the metalloids from the pre-halogen nonmetals. The "reactive" nonmetals to the right of the metalloids each have a sub-metallic appearance (C, O, Se, I).

Edge of the world line: No guesses for this one.

Klemm line: Klemm, in 1929, was the first to note the double periodicity of the lanthanides (Ce to Lu).

Lockyer line: After the discoverer of He, the first element not found on Earth.

Ørsted line: After the magnetic effects believed to be responsible for Mn having a crystalline structure analogous to white P; Tc: First radioactive metal; Re: Last of the refractory metals; "most radioactive" of the naturally occurring elements with stable isotopes. Fe: First of the ferromagnetic metals; Ru: First noble metal; Os: Densest of naturally occurring metals. The number of unpaired d electrons peaks in group 7 and reduces thereafter.

Platypus line: Tl shows similarities to Rb, Ag, Hg, Pb.

Poor metal line: Most metals (80%) have a packing factor (PF) ≥ 68%. Ga: Has a crystalline structure analogous to that of iodine. BCN 1+6. PF 39.1%. Melts in your hand. In: Partly distorted structure due to incompletely ionised atoms. BCN 4+8. PE 68.6%. Oxides in preferred +3 state are weakly amphoteric; forms anionic indates in strongly basic solutions. Tendency to form covalent compounds is one of the more important properties influencing its electro-chemical behaviour. Sn: Irregularly coordinated structure associated with incompletely ionised atoms. BCN 4+2. PF 53.5%. Oxides in preferred +2 state are amphoteric; forms stannites in strongly basic solutions. Grey Sn is electronically a zero band gap semimetal, although it behaves like a semiconductor. Diamond structure. BCN 4. PF 34.0%. Pb: Close-packed, but abnormally large inter-atomic distance due to partial ionisation of Pb atoms. BCN 12. PF 74%. Oxide in preferred +2 state is amphoteric; forms anionic plumbates in strongly basic solutions. Bi: Electronic structure of a semimetal. Open-packed structure (3+3) with bonding intermediate between metallic and covalent. PF 44.6%. Trioxide is predominantly basic but will act as a weak acid in warm, very concentrated KOH. Can be fused with KOH in air, resulting in a brown mass of potassium bismuthate.

Seaborg line: No f electrons in gas phase La, Ac and Th atoms.

Triple treat line: N = gas; S = solid; Br = liquid.

Zigzag lobby: H: needs no intro. Li: Many salts have a high degree of covalency. Small size frequently confers special properties on its compounds and for this reason is sometimes termed ‘anomalous’. E.g. miscible with Na only above 380ºC; immiscible with molten K, Rb, Cs, whereas all other pairs of AM are miscible with each other in all proportions. Be: Has a covalent component to its otherwise predominately metallic structure = low ductility. Lowest known Poisson's ratio of elemental metals. Amphoteric; predominately covalent chemistry atypical of group 2. Some aspects of its chemical properties are more like those of a metalloid.

Zigzag line: Eponymous metal-nonmetal dividing line.

Zintl line

: Hypothetical boundary highlighting tendency for group 13 metals to form phases with a various stoichiometries, in contrast to group 14+ that tend to form salts with polymeric anions.

*BCN = bulk coordination number

Sandbh (talk) 13:42, 17 September 2020 (UTC)[reply]

Oganesson as a metalloid

Og is predicted to be solid, with a band gap of 1.5 eV. On this basis, it could be expected to have a sub-metallic appearance. The predicted IE is 860 kJ/mol; predicted EA is 5 kJ/mol. From IE and EA, EN is given by

${\displaystyle \chi =(1.97\times 10^{-3})(E_{\rm {i}}+E_{\rm {ea}})+0.19.}$

${\displaystyle =(1.97\times 10^{-3})(865)+0.19.}$

= 1.89

Given, on this basis, that Og has an intermediate IE (750 to 1,000) and EN (close to 2) and is expected to be a (relatively) reactive sub-metallic looking semiconductor, it appears like it will be a good candidate for admittance into the metalloid club. In any event group 18 will seemingly need to be referred to as the helium group, rather than the noble gases group.

It’ll be a curious arrangement to have metalloids in groups 13 to 16, and 18, but not one in group 17. Astatine would’ve been a semiconductor, and hence counted as a metalloid, but for relativistic effects. Sandbh (talk)

@Sandbh: Commenting to say that I agree with your conclusion, despite coming from a very different philosophy and perspective from yours. (Normally I would continue to not comment here because the different philosophy means our conclusions usually do not match, but since I happen to be looking today and in this case they do match, here we are.) Provided that these predictions are right, I would in my preferred paradigm call oganesson a nonmetal because it would lack the delocalisation in its stable or metastable allotropes that is the one criterion I use, and guess that it looks and behaves something like silicon. As you know, I prefer to divide only between metals and nonmetals, but as you also know almost all the metalloids end up by my criteria on the nonmetals' side anyway (only Sb ends up with the metals), so I am inclined to count this as basically an agreement as I would guess Og to be definitely (although weakly) on the nonmetallic side like Si.

It must of course be noted that I would do this only provisionally, and that there is no substitute for experimental results; it is the excellent agreement with the computations with experiment for the lighter elements that makes me willing to provisionally say this.

To me "noble gases" is not a group name but a family name, so I do not think it has to a priori follow the whole group any more than "alkali metal" has to include hydrogen. Again assuming the predictions are correct, what I would do in my preferred paradigm is rename the category to "noble fluids" (to let in copernicium), and simply let it split across three groups: helium in group 2 (my IIs), neon through radon in group 18 (my VIIIp), and copernicium in group 12 (my XIId). Double sharp (talk) 15:30, 17 September 2020 (UTC)[reply]

Double sharp: On the metalloids I have advocated for treating them as chemically weak nonmetals rather than as a unique category of their own. I now recognise it doesn't matter so much how you regard them as long as the context is explained. This principle applies to the treatment of Sb, too. What happens in the literature is that due to e.g. publish or perish or educational curricula or IUPAC recommendations, authors tend to parrot one another, overlooking the benefits of diverse perspectives which, I suppose, tend to be left to the specialist literature.

There is the precedent of referring to the noble gases as the aerogens. The etymology of -gen in this case is < French -gène, ultimately representing Greek -γενής ( < γεν- root of γίγνεσθαι to be born, become, γεννάειν to beget, γένος kind, etc.: see kin). So noble gases are a kind of air, or aerogens.

This sense can be contrasted with the related sense of -gen as "generator", e.g. in the case of halogens as producers of salts. This was extended to chalcogen ("producer of copper ore"). Its further extension to pnictogen ("producer of choking") to describe the nitrogen group is awkward. It involves a change from "producer of a substance" to "producer of an effect", and only describes nitrogen.

Anyway, group 18 could instead be called the octadecagens.

Now, the convention in chemistry is to descriptively name a group according to [1] attributes shared within the group, never mind such attributes may be shared by elements external to the group; or [2] according to the nature of its progenitor e.g. pnictogens after the suffocating nature of nitrogen. For [1] there are many examples of nominative attributes shared by elements external to the Group:

• yttrium is an alkaline earth.
• nickel is a coinage metal.
• volatile metals is a good enough name for the group 12 metals relative to metals in this part of the table. Yet the alkali metals are even more volatile in their own part of the periodic table (cf alkaline earth metals or rare earth metals).
• nitrogen, relatively speaking, is a noble gas (that was how it was regarded pre- the discovery of the group 18 noble gases).

When I refer to "convention" in chemistry, I say this recognising chemistry is replete with idiosyncrasies, fuzziness, and instances of ignoring IUPAC recommendations.

Group 1 seem to be OK referred to as hydrogen and the alkali metals or H and the alkali metals or the H-alkali metals ("halkali metals"?) with the option of leaving out the H, if only the AM proper are being considered. Or go the whole honk'n' hog as hydroalkali metals, treating H as a unique kind of metal, noting the alloying capacity of H and its capacity to stand in for alkali metals proper in some compounds.

The noble fluids are presumably a sub-category of the noble elements (metals and nonmetals)? Is N included here?

Good fun eh? Sandbh (talk) 01:22, 18 September 2020 (UTC)[reply]

@Sandbh: Yes, good fun. Anyway for me it's just a hobby, so I did the above to my taste. Therefore I just answer your question about my category. ^_^ No, for me noble fluids are a category in themselves, I don't want to include the so-called noble metals because they are quite happy to stay in compounds once they're already in one. That's the same reason I don't want to include nitrogen there. I had in mind rather the typical instability of Kr and Xe compounds (even XeF₂ is strong fluorinating agent) as a guide for what should be considered noble. Yes, radon may be ambiguous because RnF₂ seems rather stable and it has been seriously proposed to get rid of Rn in air by reacting it away, so I wait for future experiments with interest. So, unless there are any more questions, I'll leave you to discuss categorisation with the others for the time being again. ^_^ Double sharp (talk) 07:37, 18 September 2020 (UTC)[reply]

P.S. Maybe indeed I should consider the placement of radon as a noble fluid to be questionable. It would fit with how I generally view polonium as a chalcogen and astatine as a halogen; they are so only sort of. Double sharp (talk) 15:37, 24 September 2020 (UTC)[reply]

@Double sharp: Painless learning placements have updated their periodic table placemat. The link is to the old version.

The 2019 version colours:

• group 12 as PTM;
• H, C-N-O, P-S-Se, as "other nonmetals";
• F-I as "halogen nonmetals";
• Po-At as PTM;
• Cn-Ts as PTM; and
• Og, in a big call, as a metalloid.

Curiously, Milt shows the nonmetals as follows:

Nonmetals

Metalloids

Other nonmetals Halogen nonmetals Noble gases

I have four spares if anybody would like me to mail them one, no charge. PM me. Sandbh (talk) 04:21, 6 October 2020 (UTC)[reply]

On chemical natural kinds (Scerri 2020)

doi:10.1007/s10838-020-09511-9

Abstract: A critique of LaPorte's views on chemical kinds, like jade and ruby, is presented. More positively, a new slant is provided on the question of whether elements are natural kinds. This is carried out by appeal to the dual nature of elements, a topic that has been debated in the philosophy of chemistry but not in the natural kinds literature. It is claimed that the abstract notion of elements, as opposed to their being simple substances, is relevant to the Kripke–Putnam approach to natural kinds and to some criticisms that have been raised against it, although I do not support the K–P account. The proposed view avoids the traditional microstructuralist approach to natural kinds. The article also addresses the question of whether natural kinds concern metaphysical or epistemological considerations. Recent attempts by chemists to modify the periodic table are brought to bear on the question of classification and consequently on whether the identification of elements is interest dependent.

The location and composition of Group 3 of the periodic table

I am pleased to note my article has been now published in Foundations of Chemistry, here (open access). About has been about nine months in the making; I only signed off on the (eighth) proof, last night. The acknowledgements section includes the following credit: "I thank…members of Wikipedia’s WikiProject Elements for their indefatigable stress-testing of an early draft of this article." Sandbh (talk) 05:19, 24 September 2020 (UTC)[reply]

Congratulations! At last it's online!--R8R (talk) 05:37, 24 September 2020 (UTC)[reply]

My sincere congratulations too on getting published. My apologies if I am still not convinced, though. ^_^ Double sharp (talk) 08:41, 24 September 2020 (UTC)[reply]

That is fine. Happy reading and brow raising! Sandbh (talk) 12:48, 24 September 2020 (UTC)[reply]

Yes, it was indeed an engaging and thought-provoking read. Double sharp (talk) 20:17, 24 September 2020 (UTC)[reply]

P.S. Added to my list of articles that mention or discuss the question. And flagged as quite long and collecting various arguments. ^_^ So, looking forward to hearing about the IUPAC project's progress. Double sharp (talk) 09:17, 24 September 2020 (UTC)[reply]

Will do. Sandbh (talk) 12:48, 24 September 2020 (UTC)[reply]

One of the authors I cited, Simon Cotton, has asked me if his book title could be corrected. In the reference list it shows as "Lanthanoid and actinoid". The right title is "Lanthanide and actinide".

Another of the authors I cited, Eugen Schwarz, has advised me of an egregious error of my own making. Wherever I refer to Ligshitz I should have referred to Lifshitz. He also asked me if it would be possible to replace "(Eugen Schwarz, pers. comm. 8 Dec 2019)." with "(Dogon & Pyykkö 2017)."

The reference details are: Dognon, J-P., Pyykkö, P. Chemistry of the 5g elements: Relativistic calculations on hexafluorides. Angew. Chem. Int. Ed. 56, 10132–10134 (2017)

I asked Springer to make these corrections as they make no difference to the citability of the doi. The have, of course, declined to do so. While the eight-proof nightmare concluded the dead have arisen as I run into the Springer Wall of Obstinacy. Sandbh (talk) 03:29, 25 September 2020 (UTC)[reply]

Congratulations!! What a shame you could't get those final fixes, but as you say, it is unsurprising. If I recall correctly, this is not your first effort dealing with a journal publisher. To what do you attribute the experience? Are there any lessons learned that would be worth sharing? YBG (talk) 06:22, 25 September 2020 (UTC)[reply]

Extending electronegativities to superheavy Main Group atoms

A few surprises; Here. Sandbh (talk) 05:34, 24 September 2020 (UTC)[reply]
Pinging Double sharp.

@Sandbh: Interesting article, but I do not agree at all with the new values for most elements. Electronegativities of Ar through Rn are too high (should be closer to those of S through Po). Ne is OK, but He should be lower than O. All chemical indications are that astatine is more metallic than iodine and the EN value should be lower, not higher as Karol gives. Radon is clearly also less electronegative than xenon (RnF₂ is mostly ionic), but Karol gives a higher EN value. Francium should be more electronegative than caesium, but Karol gives it as less electronegative. The 7p elements also seem to have way too high values: flerovium is a pseudo-shell closure, so Mc through Og values should be a lot lower (chemical intuition suggests Og around Si value at very most, and quite likely lower). Perhaps some aspect of the problem is the considering of 7s-electrons for the superheavies when from Fl onwards they should be too deeply buried to actually use. I know EN rises with oxidation state, so could the inflated EN values be a consequence of using s-electrons implying a chemically unreasonably high oxidation state? That would explain why the only new values I find somewhat reasonable are for the not-yet-discovered 8s elements: 119 with value of K and 120 with value of Ba seems at least plausible.

@Droog Andrey: What values would you give elements 119 and 120 on your scale? I previously guessed 0.83 and 0.96 on the grounds of the Pauling EN values listed at ununennium and unbinilium, but would definitely prefer to have you opine. ^_^ Double sharp (talk) 09:15, 24 September 2020 (UTC)[reply]

@Double sharp: I agree.

Karol does not provide a clear explanation as to why EN values should go up in the later superheavy p-block elements. He says:

"However, the monotonic drop in electronegativities proceeding down any group column reverses as the heavy elements are approached. This is most likely a reflection of relativistic effects in which the valence electrons are drawn in closer to the nucleus and are more difficult to “move”.

Is he saying that as the valence electrons are drawn in closer to the nucleus that atomic radii therefore reduce and therefore that the nuclear charge is more strongly "felt" and that therefore EN goes up?

I could buy that.

This does not square so well with astatine, for example. Astatine is more metallic than iodine yet iodine has an Allen EN of 2.36 whereas At is supposedly 2.5

Nor with Te (2.16 and Po (2.27) whereas we know Po forms cation in aqueous solution whereas Te does not.

Nor with Xe (2.58) and Rn (2.74), where Rn has been reported to exhibit cationic behaviour.

Something is not working here. And Karol does not shed any light on it.

I am surprised he got past referees without one of them picking up on this.

OTOH, the values for 119 and 120 are more plausible.

I've asked Eugen for his take on this since he brought Karol to my attention. Sandbh (talk) 07:08, 25 September 2020 (UTC)[reply]

@Sandbh: Relativistic effects for Og (for example) will lower energy level of 7s and 7p_1/2 but not of 7p_3/2 which is raised. And by the way the splitting is so large that it doesn't really make sense to refer to single p-orbital energies. And 7s here is lowered so much that it really should just not be counted as valence at all. Electronegativity rises with increasing oxidation state, and so I could buy these only as not-relativistic-enough values for hypothetical group-oxidation-state compounds of these elements (Nh^III, Fl^IV, Mc^V, Lv^VI, Ts^VII, Og^VIII) that, thanks to relativity, have actually no chemical relevance at all because these oxidation states are unreachable. (Except Nh^III which should still be possible as NhF⁻
₄, but a better EN value should rather reflect the more common +1 state.) That also explains partly the too high values of the 6p elements that are for not-very-common high oxidation states. This problem doesn't affect 7s and 8s as badly: just comparing comparable theoretical values, indeed Karol ends up with EN(Fr) > En(Cs) (although I think Ra can very well be below Ba), but then he mixes spectroscopic measurements with theoretical calculations in Fig. 2. Incidentally, Karol presented Fricke's extended table wrongly in an older article of his in the same journal (Chemistry International).

I'll stick with Droog Andrey's electronegativity values, myself. Although 119 and 120 don't have values yet. ^_^ Double sharp (talk) 09:16, 25 September 2020 (UTC)[reply]

Lead PT in PT article

Periodic_table

I've updated the PT in the lead of our PT article to make it more of a showcase. Please let me know how it looks. It's a jpg for now. My aim was for a better accommodation of the Ln/An; a readable legend; better use of space; restoration of the halogen terminology in some way; and a balanced look.

The noble metals are not caret-ed. The pre-halogen nonmetals are not explicitly flagged. The Notes section at the right of the legend adds a few nuances.

This is a fair summation of the literature, as we have shown it to date. I'll continue to advocate for a merge of groups 1 and 2, and Al; and for a more formal carving out of the pre-halogen nonmetals. --- Sandbh (talk) 05:05, 25 September 2020 (UTC)[reply]

@R8R, YBG, DePiep, and ComplexRational: Sandbh (talk) 07:14, 25 September 2020 (UTC)[reply]

I would merely prefer that La and Ac are colored back as a lanthanide and an actinide, respectively, because that's a part of our well-established coloring scheme. I don't think this would be particularly controversial since the existing scheme has been in place for a long while now and since we normally discuss any changes to it. My comments other that this one can wait until I have finally responded to the last Sandbh's message on the proposal to reform the coloring scheme.--R8R (talk) 07:45, 25 September 2020 (UTC)[reply]

+1 Double sharp (talk) 09:16, 25 September 2020 (UTC)[reply]

Agree with R8R. (I have reverted the edit, see below). -DePiep (talk) 09:30, 25 September 2020 (UTC)[reply]

@R8R, Double sharp, DePiep, and YBG: Oh! I forgot that one. Easily fixed. Sandbh (talk) 10:38, 25 September 2020 (UTC)[reply]

Legend style options

A few comments

• The AM cells do not appear to be the same color as their legend, but maybe that is an optical delusion on my part. At any rate, everything should match the enwiki color scheme until we change it.
• The two color bands for the lanthanoids and actanoids are truly superb. I'd say it makes this the best job of shoehorning 32 columns into 18. Much better than the grawlix. Great job!!!!
• I think the notes are much too detailed for a chart in the lede; I would leave them out unless there is a consensus to include them.
• I find the horizontal bars in the legend distracting. You could accomplish the same thing by moving the text closer to the colorbox.
• Here are some alternate layouts for the notes that include only a few lines; and some of these options would work well even without the lines I have shown.

Extended content

Style #1: Single-row, mega categories on bottom                                                                         Alkali Alkaline earth Actinide Lanthanide Transition Post-transition Reactive Nobel gas Metals Metalloids Nonmetals Notes: †: F–I = halogen nonmetals H, C, N, O, P, S, Se are sometimes called 'biogen', 'CHONPS', 'orphan' or 'other' nonmetals.   The chemical properties of these elements have not been determined. Style #2: Single-row, mega categories on top Metals Metalloids Nonmetals                                                                         Alkali Alkaline earth Actinide Lanthanide Transition Post-transition Reactive Nobel gas Notes: †: F–I = halogen nonmetals H, C, N, O, P, S, Se are sometimes called 'biogen', 'CHONPS', 'orphan' or 'other' nonmetals.   The chemical properties of these elements have not been determined. Style #3: Double-row, mega categories on top Metals Metalloids Nonmetals   Alkali   Alkaline earth   Actinide   Lanthanide   Transition   Post-transition       Reactive   Nobel gas Notes: †: F–I = halogen nonmetals H, C, N, O, P, S, Se are sometimes called 'biogen', 'CHONPS', 'orphan' or 'other' nonmetals.   The chemical properties of these elements have not been determined. Style #3: Double-row, mega categories on bottom   Alkali   Alkaline earth   Actinide   Lanthanide   Transition   Post-transition       Reactive   Nobel gas Metals Metalloids Nonmetals Notes: †: F–I = halogen nonmetals H, C, N, O, P, S, Se are sometimes called 'biogen', 'CHONPS', 'orphan' or 'other' nonmetals.   The chemical properties of these elements have not been determined.

— YBG (talk) 08:55, 25 September 2020 (UTC)[reply]

re YBG, legend styles (this preferably be discussed in a single dedicated section, but alas). The catgegories in two-row is ill advised, because it suggests another, different hierarchy, as if there is a subordination. While the full horizontal order it greatly and helpfully supports the trend! This even applies to the Ln-An order, how inviting it may be (Ln and An is not a vertical, subordering nature; it's just periods). BTW, is there any reason two rows are needed? As a detail: I think it helps and simplifies when the word 'metalloid' is repeated.

User:YBG, do I understand you prefer the 'color bands' above 'grawlix' (asterisks) as placeholder? If so, I do not agree. The astersisks do have a graphical function (not chemically), being placeholder for the graphic displacement of a set. The displacement should be clarified, not just a "find this out yourself" (like an incomplete IKEA guidepaper). As it happens, using one and two asterisks strengthens the two-row essence nicely. It could look less elegant to some, but that should not overrule a useful solution. Also, we should keep in mind that the 18-column variant is an editorial variant, not a scientific one; created for convenience(?) or old-habit. -DePiep (talk) 09:49, 25 September 2020 (UTC)[reply]

{@DePiep: On reflection, I realize that the asterisks serve an important function for accessibility which the color bands do not provide. But coloring the placeholder spaces makes the correspondence more obvious. It would be interesting to see what it looked like with the asterisks. YBG (talk) 14:55, 25 September 2020 (UTC)[reply]

Good point, YBG. I see it has been addressed in later version. -DePiep (talk) 07:55, 26 September 2020 (UTC)[reply]

• To consider: Style #4:

Style #4: Single row, meta categories in top, wide colorboxes

Metals						Metalloids	Nonmetals
Alkali	Alkaline earth	Actinide	Lanthanide	Transition	Post-transition	Metalloid	Reactive nonmetal	Nobel gas
Chemical properties of this element have not been determined

I have applied these principles and thoughts:

1. Subcategories in single row; most important. Colors in two rows = intruducing non-existant hierarchy; not even helpful or clarifying fo Ln, An (because that's what the periods are doing, not cetegories).
2. Meta-categories in top, supports "super to sub" vertical refinement (as opposed to: meta's below = 'gathering' the subcategories).
3. Also single row usefulness: use wide color blocks, as it nicely follows the trend present in the PT. This makes connection ledgend-color <--> element background way more easily to make, both directions.
4. Put names below the c0lor not next to; strengthens trend-layout (mentioned above), and reduces/solves text length issues (bonus)
5. Todo. tweak: whitespace, vertrical lines, gray color positioning, consider putting names inside color box not below?
6. Footnotes proposed (dagger etc) should & could be added separately (if at all); outer border adjust per situation

-DePiep (talk) 08:55, 29 September 2020 (UTC)[reply]

Comments (continued)

• I have reverted this change in periodic table. Please, Sandbh, strive for consensus here first. Apart from the many detailed (i.e., unrelated) changes not fleshed out, there also is the more general like what is the reason to make the changes (improvement?), and why would we leave the "general enwiki preferred presentation" we have. -DePiep (talk) 09:28, 25 September 2020 (UTC)[reply]

• I find it strange that it has not been achieved to unify AE and AEM into a single category. To me, from a little distance, it seems to be the least controversial change proposed in the last ten years, scientificaly based. Only a naming issue left. § Unification of AM and AEM. Note that I do not propose that merge, I propose a clean result of that discussion. Meanwhile, other proposed changes were added and removed at random these weeks. -DePiep (talk) 09:56, 25 September 2020 (UTC)[reply]

  I beg to differ on this one. Sorry to keep you all waiting for my response.--R8R (talk) 10:46, 25 September 2020 (UTC)[reply]

@YBG:Thanks for the tremendous feedback YBG, including the suggested legend formats. I’ll look at these closely. One thing to consider, I suspect, is the desirability of making the legend legible within the size of the lead box. Sandbh (talk) 10:33, 25 September 2020 (UTC)[reply]

@YBG: I believe I like something along the lines of scheme #3. Sandbh (talk) 11:07, 25 September 2020 (UTC)[reply]

@

WP:BOLD. I posted the new PT further to recent discussions within our project. Straight after I explained my design intent and sought comments. You can see the resulting good feedback. Thank you for your support of a Group 1-2 merge. There are three of us now. Sandbh (talk) 10:52, 25 September 2020 (UTC)[reply

]

... is the opposite of what I said. I am explicitly not !voting for the AE-AEM merge, I noted that the "easiest", less controversial and most science based change did not achieve consensus. For the other changes: yes, you can go B. I declare them controversial/no consnsus so R. And here we are, at D. -DePiep (talk) 11:07, 25 September 2020 (UTC)[reply]

@DePiep and YBG: OK so just myself and YBG are advocating for a merge of Groups 1 and 2. There is ordinarily no need for R. D will get the same result. Sandbh (talk) 11:29, 25 September 2020 (UTC)[reply]

@DePiep: I alerted other professional non-WP colleagues (~80) with an interest group in periodic table and chemistry education matters, by sending them a link to the PT article. A pity the R now makes it look like I did not know what I was talking about. Would you consider undo your R please, pending the next iteration? Sandbh (talk) 11:41, 25 September 2020 (UTC)[reply]

re: no it does not look like that, and I see no need to turn it that way. As I described, the changes are without consensus. That's all. I added that the discussions are random and chaotic, and I still do not see why independent topics are not discussed and concluded independently. Why is there not a start describing what is wrong with current presentation, or up for improvement? -DePiep (talk) 12:31, 25 September 2020 (UTC)[reply]

(ec) @

Non sequitur 'conclusions'. -DePiep (talk) 11:43, 25 September 2020 (UTC)[reply

]

@DePiep: If you had been following the discussion about AE/AEM you would not have to ask me this question. You expect me to do your homework for you. You are quick to object and revert, after people like me have put in the hard yards, without understanding the context for what you object to or revert. As you do not follow the converstations, the result is that you are part of the problem, not the solution. I will no longer put up with this unhelpful WP:CIVIL behaviour of yours and from now will call it as I see it, including at WP:ANI. What happens here is a product of what people put into it. You can like it, lump it, or make your contributions. If you are getting tired of this way of discussing things within our project you can leave anytime, and free up the rest of us to get on with it. Sandbh (talk) 05:55, 26 September 2020 (UTC)[reply]

@

personal attack, and not containing *any* argument). In fact, you implicitly admit you used non-existing conclusions, admitting by the changes you made to you proposal today. Some explicitly following my remarks. Also, I can point you to my(!) constructive contribution when I noted that the AE-AEM merge is 'easy' to achieve; a note you have incorporated. -DePiep (talk) 08:14, 26 September 2020 (UTC)[reply

]

@R8R, YBG, DePiep, ComplexRational, and Double sharp: I've updated the lead periodic table. Comments welcome. DePiep please do not R. This table is based on what I understand, based on comments made here, to be consensus by R8R, YBG, Double sharp, and myself. D please if you still have concerns. Sandbh (talk) 13:12, 25 September 2020 (UTC)[reply]

Sandbh Please list where you prove consensus for each of the detailed changes. -DePiep (talk) 13:25, 25 September 2020 (UTC)[reply]

@Sandbh: Looks pretty good overall, though I still have a few comments:

• I'm not aware of any common use of the term "halogen nonmetals" as said in the legend; every source I know simply calls them "halogens", so I'd think it better to stick to that.
• I would not support a merger of groups 1 and 2, because to my understanding, their chemical characteristics are somewhat different and this is reflected in the majority of sources I've read.
• Because of the terminology involved, I feel it is more confusing to readers to say "La and Ac wear two hats", simply because of the visual disconuity of TM–14 Ln/An–9 TM and the idea that La and Ac would not be part of the categories to which they lend their name. I don't think average readers want to get embroiled in the Group 3 debate, and neither should we. A simple PT should not reflect a lack of consensus both on WP and in the scientific community, so we can display group 3 as is, but leave Ln as 57–71 and An as 89–103.
• As far as formatting, was it your intention to have groups 11 and 17 noticeably wider than the rest?
• I also think the table looks better with an external border (not just the ones between element cells).

If I see anything else, I'll add it to this list. ComplexRational (talk) 13:33, 25 September 2020 (UTC)[reply]

As has been pointed out half a dozen times, "halogens" is used for group 17 full stop. Injecting the term into the categories, as a venn-description, is not helpful (such details cen be in the dedicated article or section, say

halogens). In general, Sandbh nor any other editopr has explained let alone convinced why these details should be added to the first and foremost PT in enwiki. -DePiep (talk) 15:01, 25 September 2020 (UTC)[reply

]

I apologize but no. That's a common misconception. The term "halogens," strictly speaking, is not about the group, it's about a set of elements in that group. The difference is element 117, tennessine: it is not a halogen by default (as a group 17 element), it may be one or it may not be one depending on what properties it will display once somebody checks. The thinking in the field is that it won't be a halogen (see also note b in tennessine). The Red Book defines the set as consisting of F, Cl, Br, I, and At, rather than as a synonym of "group 17 element" (granted, the book was written before element 117 was first synthesized, but still their definition is on per element basis). The same also applies to every other group label in Template:Periodic table except those for groups 1 and 2, which may hint that maybe getting rid of those names would be better for an encyclopedia, or maybe we could use a comment or a note instead to clarify this if we do want to keep these group names nonetheless.--R8R (talk) 16:16, 25 September 2020 (UTC)[reply]

(OK. A very smart and sensitive response, worth rethinking). -DePiep (talk) 22:04, 25 September 2020 (UTC)[reply]

That's not a given I think. I agree with R8R's point of view that "halogen" and "group 17" are something different: to me, the former implies some common properties, that it is a category. That such a category must be united by some properties (although good luck finding what the properties are and whether the properties define the category or are just things an already defined category's members have in common). And I can show examples with titles like "Astatine: Halogen or Metal?"" But is that what IUPAC thinks? They talk about "collective names for like elements" indeed, rather than saying "groups". But in 2005 excluding Ts doesn't mean anything because it's not a thing yet. If it had been discovered, would they have excluded it? I can't possibly answer that and neither can anyone who wasn't involved in writing that passage in the 2005 Red Book. Indeed IUPAC itself has later in 2016 referred to "new elements of the halogen and the noble gas groups": that's the recommendation that gave us "tennessine" and "oganesson" rather than "tennessium" and "oganessium". So, is "halogen" a group or a category? I don't think we should issue such a warning that halogen as the whole group 17 is a misconception because the literature is not clear about that. Even if I agree that it's not a good conception. I also don't think we should say outright that they are the same either. That's of course about what is done on Wikipedia. Anyway, here is the text from the Red Book:

“

The groups of elements in the periodic table (see inside front cover) are numbered from 1 to 18. The elements (except hydrogen) of groups 1, 2 and 13–18 are designated as main group elements and, except in group 18, the first two elements of each main group are termed typical elements. Optionally, the letters s, p, d and f may be used to distinguish different blocks of elements. For example, the elements of groups 3–12 are the d-block elements. These elements are also commonly referred to as the transition elements, though the elements of group 12 are not always included; the f-block elements are sometimes referred to as the inner transition elements. If appropriate for a particular purpose, the various groups may be named from the first element in each, for example elements of the boron group (B, Al, Ga, In, Tl), elements of the titanium group (Ti, Zr, Hf, Rf), etc. The following collective names for like elements are IUPAC-approved: alkali metals (Li, Na, K, Rb, Cs, Fr), alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra), pnictogens8 (N, P, As, Sb, Bi), chalcogens (O, S, Se, Te, Po), halogens (F, Cl, Br, I, At), noble gases (He, Ne, Ar, Kr, Xe, Rn), lanthanoids (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), rare earth metals (Sc, Y and the lanthanoids) and actinoids (Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr). The generic terms pnictide, chalcogenide and halogenide (or halide) are commonly used in naming compounds of the pnictogens, chalcogens and halogens. Although lanthanoid means ‘like lanthanum’ and so should not include lanthanum, lanthanum has become included by common usage. Similarly, actinoid. The ending ‘ide’ normally indicates a negative ion, and therefore lanthanoid and actinoid are preferred to lanthanide and actinide. 8 The alternative spelling ‘pnicogen’ is also used.

”

Not planning to comment on the proposed changes now, sorry. I do not have the time to do so and only remark here because I was summoned to the previous discussion. Maybe later, or maybe not. ^_^ Double sharp (talk) 22:23, 25 September 2020 (UTC)[reply]

@

WP:BRD

perfectly, which your restoration does not. The fact that you notified 80+ others is immaterial. You can re-notify them with a link to the graphic or with a link to a particular archived version. I think the best thing for you to do would be to self-revert. I myself will not revert it, but I would support anyone else who wishes to do so. I find these specific problems with your graphic

1. Your inclusion of the information about "pre-halogen nonmetals" and "halogen nonmetals" is more detail than belongs in the lede.
2. Furthermore, it reeks of promoting your own hobby horse that has not achieved a clear consensus.
3. Inserting it as an image makes it impossible to guarantee that the color scheme is consistent with the
   WP:ELEM
   color scheme
4. Inserting it as an image makes collaboration by editing impossible.
5. Inserting it as an image makes you the gatekeeper of any changes to it.
6. Together these make it seem as though this edit is an attempt at
   WP:OWN
   . Having spent years collaborating with you, I am quite sure this is not true, but the appearance is there. It should have come as no surprise that your edit was reverted. I repeat my statement above: it would be best if you self-revert your change.

DePiep brings up an important point that our discussions have been disjointed. I will own up to having been a major contributor to this problem. When I have been away from this page and see 20+ edits, I try to find the best place to insert my comments. Much of my recent editing has been on my phone. The small screen plus the lack of section links makes it very difficult for me to see context and so I have been the biggest contributor to the topic drift especially in the AM+AEM discussion. For that I beg the forgiveness of my friends here at WP:ELEM. YBG (talk) 14:50, 25 September 2020 (UTC)[reply]

Well described, YBG. As for the last paragraph: no need to look for 'blame'; from here (from any moment actually) we still can reorganise the multiple independent discussions so that each can conclude crisply by itself. -DePiep (talk) 14:56, 25 September 2020 (UTC)[reply]

When I wrote +1 above, I simply meant to express agreement with R8R that La and Ac should be coloured as members of their eponymous categories (Ln and An). That's been standard for a while, it is what IUPAC defines the Ln and An as, and I don't see any consensus to change that. R8R also mentioned that he has some other comments that are pending his response to some comments above, and I would rather wait for him to write them before I decide whether to say something about the other proposed changes. My apologies for not expressing this clearly. Double sharp (talk) 15:12, 25 September 2020 (UTC)[reply]

Thanks, Double sharp. But actually our "talk & make consensus" conference here has died. -DePiep (talk) 21:26, 25 September 2020 (UTC)[reply]

• Again, Sandbh: [3]: Please list where you prove consensus for each of the detailed changes. -DePiep (talk) 21:36, 25 September 2020 (UTC)[reply]

@DePiep: Why is it that within our project, when there is an effort to improve something based on discussion, you shoot first and ask questions later rather than discuss first? Sure, there is BRD and I would've thought that would be the option of later or last resort rather than first choice.

Regarding consensus, the sequence of events was roughly 1. In the context of discussion within our project, I updated the graphic. 2. I told WP:ELEM about it and why. 3. R8R and DS asked for a minor easily accommodated change, that is all. 4. YBG suggested some other really cool options for the legend. 5. I took these comments by R8R, DS and YGB as indicating consensus for the change, subject to some modifications, which I enacted. 6. CR chimed in saying he was basically happy with the graphic, and provided some comments which I just read now, and will look at again.

How much more support do I need before being able to interpret these comments as consensus? Consensus does not require unanimity.

You expressed some concerns and decided to revert on this basis, even though consensus does not require unaniminity. Our project does nor revolve around and is not contingent upon, your concerns. You are entitled to express them here. In

WP:CIVIL terms I object to your drive by shoot first (twice in this case) and ask questions later approach, without doing your homework. Sandbh (talk) 04:18, 26 September 2020 (UTC)[reply

]

@

WP:OWN

.

What a load of Australian cobblers. Collaboration impossible eh? What do you call how I incorporated your legend option #3 into the graphic? I am the gatekeeper eh? Let us ban all graphics out of gatekeeper concerns. You are right in your experience of collaborating with me over the years, which has been productive and enjoyable. So why the need to stoke to fire in the first place? What do you reckon that gained. WP:CIVIL?

Why is it necessary to waste time on this drivel? Not on the creative aspects, but on reverting and needing to re-explain one's actions. What happened to an assumption of good faith? Do we have to go "ready-aim-fire" each and every time? Is their no room for "ready-fire-aim", based on good faith and an iterative collaborative approach to improvement? Sandbh (talk) 04:26, 26 September 2020 (UTC)[reply]

@Sandbh: As I have re-read my post, I see that I used some intemporate and uncivil language; "reek" immediately jumps out. Please forgive me this.

What I was trying to say is that I believe you are being collaborative, but that these points together could make it appear that you are taking a WP:OWN attitude. I believe we should not only not take ownership, but also bend over backwards to not appear to take ownership.

(And I believe that we should not only be civil, but bend over backwards to avoid appearing to be uncivil. In that I failed.)

My two main concerns are

1. I fail to understand why there should be so much detail in the legend for a lede graphic. The lede, after all, is meant to be a high level summary. If something must be said (and I am not convinced that it is needed), why not just use something like in for the caption: "Authors differ in many aspects of the periodic table: the placement of hydrogen, in the placement and composition of group 3, in the membership of the different categories, and in how many categories they recognize." This would leave the legend to be simply a legend. Anything more seems to me to be highlighting minutae that does not belong in the lede.
2. Secondly, I am unwilling to trust my eyeball judgement that these colors match those of our {{element color}}. There are many places where colors could get skewed in the process of creating graphics.

YBG (talk) 06:10, 26 September 2020 (UTC)[reply]

@YBG: later on we can check adherence to {{element color}}. Dropping the AE-red is a good choice for access reasons. -DePiep (talk) 08:20, 26 September 2020 (UTC)[reply]

@

WP:AUTHORITY. -DePiep (talk) 07:54, 26 September 2020 (UTC)[reply

]

I want to be clear about what I said. I didn't express support for the new picture by Sandbh. I gave it merely a brief look and I thought it was fine in accordance with

WP:BOLD, if we take the issue of coloring La and Ac aside. I expected I would have to give more comments in the future (I had yet to formulate them), but only one thing needed to be pointed out quickly. The statement I made does not imply my support. This statement does not imply my opposition, either. I have simply not looked closely enough yet. There seem to be more problems with the picture and the addition of the picture has been reverted, something I have not assessed, either.--R8R (talk) 10:18, 26 September 2020 (UTC)[reply

]

I want to also be clear that my "+1" indicated support for what R8R said. I had not looked closely enough yet to decide if I supported or opposed the change at the time I wrote that: I simply saw that the issue of colouring La and Ac was something that needed to be pointed out and agreed with R8R. Double sharp (talk) 11:02, 26 September 2020 (UTC)[reply]

Latest proposed iteration

Extended content

​​​​​ I did the following:

1. checked the legend colours for matching (YBG)
2. checked the column widths (CR)
3. added a dagger to group 3 and adjusted the legend (CR)
4. changed the group 17 dagger to a double dagger
5. added an external border (CR)
6. added Z numbers to the Ln and An colour bands (DS; YGB).

A few remaining items of interest:

1. I gather YBG remains somewhat concerned about the note re H, C-N, P-Se
2. What to refer to F−I as: halogens or halogen nonmetals?
3. R8R has hinted maybe we could merge AM-AEM and mention the group names in the note
4. ComplexRational is not so sure about such a merge.

--- Sandbh (talk) 04:08, 26 September 2020 (UTC)[reply]

Extended content

---

​​​​​ Please consider Version 4, as requested by Double sharp, with two non-noble nonmetal categories. The green colour for the putative "pre-halogen nonmetals" is apt, given the seven linked biogeochemical cycles, one for each of the pre-halogen nonmetals. Compared to version 1, above, I like that the green "tones down" the field of yellow; the two colours go well together. The green of hydrogen even sits well next to the red of lithium.

As insightfully suggested/requested by Double sharp, the notes are now essentially confined to the two IUPAC areas of interest.

The "pre-halogen" name itself is not fixed.

I checked with a few chemists, via

WP:CHEMISTRY

, and they raised no objections to it.

This term will soon appear in two separate articles: (1) "Chemistry in periodic tables" by Cao C, Vernon RE, Schwarz WHE, & Li J; and (2) "The remarkable chemistry of the pre-halogen nonmetals", authored by me and submitted for publication in another journal.

If reputation counts for anything you cannot go far past Schwarz in terms of the periodic table literature. Scerri notes what Schwarz says about periodic table matters.

In terms of me, the purpose of these articles is not so I can cite myself (which is allowed by WP policy, in any event).

Rather, the purpose is to clarify the classification-science situation in the literature re the terms "other nonmetals" or "orphan nonmetals", implying these nonmetals, as a category, represent the scraps. In fact, these nonmetals have more shared diverse properties than any of our other categories. All these properties are set out in the literature.

I acknowledge YBG would prefer fewer categories. --- Sandbh (talk) 04:22, 27 September 2020 (UTC)[reply]

Extended content

Version 2 merges groups 1 and 2, and provisionally calls them "unnamed" metals, pending something more acceptable. Included are notes re: the status of H and the rest of the non-halogen-non-noble nonmetals; and which elements are AE and AEM. Sandbh (talk) 05:22, 26 September 2020 (UTC)[reply] Version 3 as requested by User:DePiep and User:Double sharp. Will fix errors tomorrow. Sandbh (talk) 13:55, 26 September 2020 (UTC)[reply]

More remaining items of interest:

5. Too much details for overview image (YBG)

6. Legend in two (three) rows is confusing and gives wrong suggestion (DePiep)

-DePiep (talk) 08:01, 26 September 2020 (UTC)[reply]

• I note that the AE-AEM merge was not concluded in § Unification of AM and AEM, and R8R has made explicit objections even in this thread. I find it disappointing, and frustrating the discuss-process, that such a change has not been fleshed out before being implemented here. -DePiep (talk) 08:33, 26 September 2020 (UTC)[reply]

@DePiep: I am disappointed and frustrated and exasperated that you are unable to consider an idea without it being discussed, processed, and fleshed out before being posted here. Now that I’ve posted it here, discussion, processing, and fleshing can follow. Do you understand what I am saying? Sandbh (talk) 11:09, 26 September 2020 (UTC)[reply]

re Sandbh: no I don't understand. Yes I can consider an idea &tc, but I oppose that an undeveloped idea is published. -DePiep (talk) 20:59, 26 September 2020 (UTC)[reply]

@R8R, YBG, and ComplexRational:

@DePiep: We see things differently.

I think it is fine to post an updated image to an article, and to develop it from there, and once it settles, to attend to other changes that may be required. For one thing it increases the exposure of the update, beyond our small project circle, to additional commentary.

Having said it's fine to do this, it's certainly not a habit of mine. But it can be a refreshing way to break up or challenge a log jam.

You oppose this approach. So much so that you will double revert, in breach of civil behaviour, the more so since you did it to a fellow project member: "Et tu DePiep?".

At least within our project, please consider this WP advice: Don't revert due solely to "no consensus" aka Don't be a jerk against boldness.

Another way of putting this is BDR, rather than BRD. When WP:ELEM members are bold, I expect they do so thoughtfully, in the light of a context or discussions within this project, which is something you ignored when you reverted me and when you revered R8R. If you have a problem with a bold edit by one of us then I ask you to consider discussing it here first, unless the bold editor said to please go ahead and revert if you want to, as I did with you recently. Having done that, if you remain unconvinced, go ahead and revert.

Of course you can choose to ignore everything I said here. You won't win any friends, however. Quite the opposite. Sandbh (talk) 23:31, 29 September 2020 (UTC)[reply]

@Sandbh: Please do not take my "+1" reaction to R8R's post as a sign that I have no other objections to this change. I do. I was not originally planning to comment here, but the cat is out of the bag since I already wrote the +1, so let's just do it. So let me just say what I think. And I try to do it very civilly.

Number one. I don't see why we should have such notes at all for the different categorisation possibilities. There are tons of possible categories (pnictogens, chalcogens, rare earth metals, noble metals) and I don't see why the category {H, C, N, O, P, S, Se} is so much more important than these others that it must be mentioned in the lede periodic table.

Number two. I really hesitate to say this for fear of re-provoking the holy war. But there is really no way around it, so again, let me try to do it as civilly as possible. These differences in categorisation are not to my knowledge a serious debate in the scientific community: everyone seems to have no problem going their own way, and there has been no IUPAC project to determine which elements belong to which category, and to my knowledge no one is calling for IUPAC to settle it. Yet some are listed in detail in the footnotes. And yet, such a prominent argument in the literature as to the very composition of group 3 that has such a IUPAC project is not apparently worth mentioning at all in the footnotes. Even though this dispute exists even for people who don't show any colour categories at all. In fact it seems to be outright avoided by calling La-Ac "also recognized as transition metals". Without also mentioning that for people who believe in group 3 with Lu in it, this would apply to Lu-Lr. Why is there this difference?

Note that, while I freely admit I did not behave very well when trying to get support for the change to Lu-Lr form here, I did not change the lede to show it. I surely did add some content to the section of

undue weight

given to the argument, there is no trace of the dispute at all in the lede. No: I tried to get it through proper channels, i.e. discussion. I did not do it in a very nice way, but I kept the issue of changing the default to the discussion pages. Not a single periodic table visible in the mainspace was changed by me (you can check).

Now, there was explicitly not any consensus to change things back to Lu-Lr, so I gave up the idea to do that. That's not to say I don't support it anymore: I still very much do. If I was writing my own book about periodicity, you can bet that the table I draw would have Lu-Lr, and that I'd use that as a default for everything other than discussing the development and history of the periodic system. Including covering group 3's descriptive chemistry (if I went that far into details when writing this hypothetical book) as Sc-Y-Lu-Lr and not mentioning La and Ac at all other than as secondary-related guests like Al. But I don't change it here on Wikipedia because I have no consensus to do it and because Wikipedia is founded on consensus. And note that I did not do it even though I had a majority at one point (when Officer781 and Dreigorich had chimed in but the denizens of

WP:CHEMISTRY

as well to confirm if there is a wider consensus for it, other than between half a dozen people who already know each other pretty well (me, you, R8R, DePiep, YBG, CR).

Not to mention that the consensus should be founded on discussions of what is in the literature rather than what the literature should be. What WP should show is what the most relevant literature says. If it says something, put that. If it is internally divided, say that. Okay, yes, there is some room for interpretation here regarding how the literature should be reflected and what the most relevant literature is; but that must be the foundation.

Where are the citations for this? Where is the consensus? Sure, consensus doesn't require unanimity, but (1) how much does a non-unanimous consensus mean if it's literally among six people and (2) do you actually have a consensus in support of the table as you have it? YBG wonders why the notes have to be so detailed, R8R says he has comments pending. Even if the others (I exclude myself as I didn't participate in the earlier stages) agreed with you, you'd only have 3/5 which is not a very strong consensus mandate among five people! Without a clear consensus for such notes in the first place, why are you putting them in the lede section? Here's one short note that I'd support and could be put in the caption: "The table below shows a common layout with colours representing some commonly used categories of elements. Other layouts and other categories are sometimes encountered and are described below." Done. Why go into so much detail in the lede just for the categories you're currently supporting? Instead of for "polyatomic/diatomic nonmetals" which seriously appear in some books that probably copied from Wikipedia when we had them?

I'm not saying that you're pushing a hobby horse, but I really hope you can see why YBG used those words. You don't have a clear consensus, and your proposed categories don't seem to be any steps above other possible ones. Polyatomic/diatomic appear in the literature now; pnictogen/chalcogen appear as IUPAC-approved; rare earths appear as IUPAC-approved. And the whole group 3 dispute that has gotten significatly more recognition than any category dispute thanks to the IUPAC project is totally not mentioned at all. Please, tell me what the difference between these things and the ones you put in is, other than whether you support them or not. If you can find one, then please explicitly say what it is to assuage concerns. And if you can't; well, indeed YBG was not appearing at his most civil, but can you at least see why you're getting such comments?

The bottom line is: we all have our biases. And maybe indeed we should clarify these biases by drawing somewhere exactly how we'd draw the periodic table if we had total editorial control over a project. I did it already. But please: let's not have them affect what we do for Wikipedia. Let's not even give the impression of having them affect what we do for Wikipedia. And note that I'm not saying your bias is affecting you. In fact, I want to hear something about why your proposed categories are more important than others and deserve such a mention in the notes, so that there is a better explanation for why they are the ones being raised up and not others. And then we can get a more complete picture for consensus to either follow or not.

As for the terms themselves: I am very wary of creating two-word phrases even if they are just descriptive because of the rather insidious tendency in English for any short phrase repeated often enough to sound like it is a term in itself. Already "reactive nonmetal" is getting to that level. (Well, reactive compared to what? Anything is reactive compared to neon, but is silicon by itself a "reactive nonmetal"?) Frankly I would rather return to the oldest colour scheme: other nonmetals, halogens, noble gases. Yes, there is astatine, but as I said above there's some use of "halogen" that implies "not a metal" even if IUPAC doesn't do it that way. If IUPAC can say "noble gas group" to include Og, and yet an article can say "Is Element 118 a Noble Gas"?, then I think the old scheme is defensible even if the halogens are taken without astatine. Or maybe even "other metal" to eliminate the wrangling over aluminium and whether it really can be called "post-transition". At least one advantage of "other" category names is that they are obviously not terms in themselves. Yes, I know, Theodore Gray says there should be a better name than "other metals", but: if it's just a should be, and there isn't a clear such better name, then I don't think it's our position to create one.

I'm not interested in creating drama. I would prefer you to read this and think about how you come across and why you got the responses you got, certainly. But if you think this is too far, if the result is a reply similar to what YBG got, then I will simply drop out of the discussion again and leave the others to it: it's not worth fighting hard over. Double sharp (talk) 10:03, 26 September 2020 (UTC)[reply]

@Double sharp: It is good to hear from you. I’ll try to be brief.

1. I see this happen all the time. Somebody makes a good-faith change based on discussions. The sky then falls down. Participants and non-participants object on the basis of not liking this or that. A revert follows. Whatever progress was made is undone. Stagnation sets in. God spare me.

2. I have discussed categories ad nauseum, and the history of how we got to where we are now, and the views of participants. This includes our traditional three-way split of the non-noble nonmetals; R8R’s support for same; and the dislike of the literature-based term “other nonmetals”, which is why we reverted to two categories.

3. That is basically why I noted the special status of H, C, N, O, P, S, Se, anchored as the relevant attributes are in the literature.

4. I am very happy to note something about Lu and Lr! That is a top suggestion! I recall ComplexRational spoke against this however?

5. Re consensus I already explained this. Here it is once more: Regarding consensus, the sequence of events was roughly 1. In the context of discussion within our project, I updated the graphic. 2. I told WP:ELEM about it and why. 3. R8R and DS asked for a minor easily accommodated change, that is all. 4. YBG suggested some other really cool options for the legend. 5. I took these comments by R8R, DS and YGB as indicating consensus for the change, subject to some modifications, which I enacted. 6. CR chimed in saying he was basically happy with the graphic, and provided some comments which I just read now, and will look at again.

Now there is a repechage from all and sundry, including your self. God spare me. I make a good faith change, based on discussion here, including multiple references to the literature. I alert everybody as to basis for doing so. What happens? DePiep invokes the nuclear option. The sky falls down. A pile-on ensues.

6. I compiled the COPTIC database. I analysed the nature of categories in a Z = 60 sample of general chemistry textbooks. I posted a table of my results and my analysis. I draw on the ngram statistics as a secondary source. That is the essentially the basis for the proposed categories. And that is seemingly still not good enough.

7. I do not like “reactive nonmetals” either. It now needlessly obfuscates information. “Other nonmetals” would do as a default, as useless as a term it is, presuming we cannot do better, noting “other” ^_^ options are in the literature. I don’t mind what we do with aluminium. It sits well with pre-transition metals. It can sit well as an outlier PTM. As long as we explain the context in the main body of the PT article. That is another good idea for inclusion in the PT article. Some mini-bios of each of the categories.

8. YBG has apologised to me personally and here. That is the end of that matter.

I trust the above addresses the key aspects of your post. I’m not interested in a holy war either. With the exception of DePiep, I intend to avoid using the expression “you” wherever possible. Not “you” as in you DS. “You” as in focussing on someone’s actions rather than the content involved.

I’ll try banging my head some more against the WP:ELEM Wall of Let Nothing Pass, about all of this. I thought I had made progress with the first new graphic and feedback I received about that, as set out above. That was until DePiep needlessly resorted twice to D rather than T. What the hell did you (DePiep) think that would resolve? Yes I am still mightily pissed off with DePiep’s behaviour and I may well yet refer his recent behaviour to WP:ANI. Sandbh (talk) 12:46, 26 September 2020 (UTC)[reply]

@Sandbh: Okay, it's good to hear that the matter with YBG is resolved. And good to hear that you're happy to say something about the group 3 issue in the footnotes. ^_^ I like form 3 better than the previous ones.

Green and yellow nonmetals

Now, personally I'd prefer actually explicitly dividing into green "other nonmetals" and yellow "halogens" on the image and giving up that footnote. Or make it "halogen nonmetals" if we really want clarity (although I'm not sure we need it because the literature doesn't seem very sure about whether "halogen" is a group or a category). "Reactive nonmetals" we both don't like anyway, and since this is literally what we had at the start before we started such categorisation megadiscussions, I don't see why it should be a big problem.

Aluminium is a more minor issue. Some people call it post-transition, it can sort of be seen this way on the grounds of it being to the right of the d block groups. So it can stay the way it is even if I don't really like it.

Now the La-Ac vs Lu-Lr issue. I think this is one that really needs to be a footnote because IUPAC has a project sorting it out, unlike all the others. I am not completely happy with the current footnote, because La and Ac as transition metals (which IUPAC defines as d block possibly excluding group 12) is something that only La-Ac proponents will agree with. Lu-Lr proponents will for sure want to include Lu and Lr instead. So I would prefer the footnote to read "Whether group 3 contains Sc, Y, La, and Ac or Sc, Y, Lu, and Lr is under review by IUPAC. The heavy members of group 3 are also known as transition metals." That seems to be a correct assessment of the situation: it's not explicitly La and Ac, but whatever the author thinks the heavy members of group 3 are (so, if we were writing externally, La-Ac for you and Lu-Lr for me). And that's the way it can stay until IUPAC says something.

Finally, since we've freed up space, we might as well show the other major disagreement that IUPAC sees fit to comment on in the Red Book, and add a footnote on group 12 saying "Some authors consider group 12 elements to be transition metals." (Personally, I would favour going back to doing that as we used to, but let's leave that as a later issue and deal with one thing at a time.) Or maybe "Some authors consider Zn, Cd, and Hg to be transition metals" (since we really don't know what is going on with Cn yet; if it really has the properties calculated for it, it will be problematic for our categories, so we wait and see).

Putting it all together, we'd be back at the old ten categories plus "unknown", we'd have green back on the table, and we'd have reserve footnotes only for disagreements that IUPAC sees fit to comment on:

1. Whether group 3 contains Sc, Y, La, and Ac or Sc, Y, Lu, and Lr is under review by IUPAC. The heavy members of group 3 are also known as transition metals.
2. Some authors consider Zn, Cd, and Hg to be transition metals.

That seems quite fine to me. So let's see what the rest of us think of that. Double sharp (talk) 18:23, 26 September 2020 (UTC)[reply]

@Double sharp: Based on a quick read, that's well written; I believe we may be in agreement, as happens from time to time ^_^. That's another good idea about group 12 you have. More to follow when I have some time to properly study what you've posted. Sandbh (talk) 00:14, 27 September 2020 (UTC)[reply]

@Sandbh: I think we are in agreement regarding how WP should present the information, based on the current consensus that La under Y should stay as a default for now. So, your V4 is very nice. ^_^ Just a couple of things:

(1) I think it's better to explicitly say "Zn, Cd, and Hg" instead of "Zn-Hg" just to make it clear that this is a vertical range and not a horizontal range. After all: this is the lede of the most basic article about the PT, so maybe let's try to state things a bit explicitly since it doesn't take too much more space.

(2) I am not sure it should be "pre-halogen nonmetals". Okay, the name is similar to "post-transition metals", I get it. The trouble is that the other names are standard categories, more or less (post-transition is at least semi-standard; not used by IUPAC but still pretty common), but pre-halogen is not. Or at least not yet. And there is the little point that I mentioned that if you repeat even a descriptive phrase often enough it begins to sound like a standard term in itself. To better reflect the literature as it stands (which so far does not seem to have any standard word for these elements) I think it may be more expedient to go for "other nonmetals". We can periodically revisit it in case a name, such as "pre-halogen nonmetals", gains traction.

Yeah, that's about all that's left. Double sharp (talk) 09:22, 27 September 2020 (UTC)[reply]

@Double sharp: Excellent. I changed the Zn-Cd thing only to save space/prevent a line break. I'll change it back. I agree your support for other nonmetal. I'll change it back to that. After that I'll see if I can think of something better, which I expect will be mission impossible! I can only hope to surprise myself. Of course! That's it. The impossible nonmetals, featuring lightweight hydrogen (flight); fecund carbon (makes the villain's noses grow long); inert nitrogen (imperturbable: vulnerable to lithiumite); powerhouse oxygen (muscles of steel); smelly sulfur (villains run away); pyrophoric phosphorous (villain costumes catch fire); and mysterious selenium (does anybody really know what the mysterious capabilities of Se are? I'm thinking Doctor Strange here.). Sandbh (talk) 13:19, 27 September 2020 (UTC)[reply]

@Double sharp: As requested. Further, I've added a note re the other nonmetals, in alphabetic order, for your consideration.

In the literature, hydrogen, and the nonmetals in relevant part of the PT on the right, excluding the halogens, have actually been referred to as light nonmetals on account of their small atomic radii and associated capacity to form "interstitial" compounds. This includes B and Si but we are not treating these as nonmetals, per se. Selenium is a borderline interstitial-compound-former (Goldschmidt 1967, Interstitial alloys, p. 43). Curiously, it has a density less than the arbitrary "heavy" metal cutoff of 5 g/cm³. Sandbh (talk) 04:55, 28 September 2020 (UTC)[reply]

@Sandbh: That's nice! I like V5 better than V4.

Note on the other nonmetals

Part 1

I still have reservations about the note on the other nonmetals though. Are any of the alternative names very common yet? If they're not, then I'm not sure we should put them in the notes here on a par with the IUPAC-acknowledged disagreements on groups 3 and 12. This is supposed to be the lede table, so I'd rather not give more complexity than is really needed. After all, there are disagreements with other categories as well, as well as many different ways to divide up the nonmetals, but we couldn't possibly list them all. Of course we can talk about this when the nonmetals are the point, but I think this note is not really needed here. After all, there is a similar problem with the naming of the post-transition metals category (it's not IUPAC-approved and there are many other names for similar sets), but we don't go into it. Double sharp (talk) 11:03, 28 September 2020 (UTC)[reply]

@Double sharp: The name light nonmetals is relatively common, compared to the alternatives. I've appended a chronological list of extracts from the literature. I stopped after thirty. Table 1 sets out the associated fields of study.

Table 1: Fields of study in which the term
light nonmetals is found, per the literature search (below)

Alloys Applied chemistry Biochemistry Cage compounds Ceramics & refractories

Crystallography Descriptive chemistry Energetics General chemistry Geochemistry

Hydrogen storage Intermetallics Materials science Metallurgy Mineralology

Nanochemistry Physical chemistry Solid-state chemistry Spectroscopy X-ray imaging

That is impressive coverage.

In my literature search results I included the details for Goldschmidt (1967), as previously cited.

Williams (1981), in his Royal Society Bakerian lecture, concisely refers to the light nonmetals as H, C, N, O, P, S and Se.

I've accordingly updated V5, as V5a. How does it look now? It looks very clean to my eye. Sandbh (talk) 06:33, 29 September 2020 (UTC)[reply]

Chronological list of extracts from the literature containing the term light nonmetals

• Hodgkin DC & Pitt GJ 1949, Crystallography, 1947, 1948, and 1949, Annu. Rep. Prog. Chem., 1949,46, 57-85, p. 67: "Compounds between the transition metals and the lighter non-metals. Interstitial Compounds.---The hard metal-like phases formed by the transition metals between non-metals (such as boron, carbon, nitrogen, and to some extent oxygen and silicon)." [2]
• Bokiĭ GB 1960 Introduction to Crystal Chemistry, vol. 2, Moscow University Publishing House, p. 338: "A second group of compounds of character intermediate between intermetallic and inorganic is composed of compounds of metals with light non-metals."
• McWhan DB 1961, Crystal Structure and Physical Properties of Americium Metal, Lawrence Radiation Laboratory, p. 8: "Unfortunately, at present, there is no convenient way of detecting trace quantities of the light nonmetals such as oxygen and nitrogen in submilligram samples of heavy metals." [7]
• Akademii͡a︡ nauk SSSR. Institut metallokeramiki spet͡s︡ial'nykh splavov, Grigoriĭ Valentinovich Samsonov, 1964, Analysis of High-melting Compounds, Translation Division, Foreign Technology Division, p. 3: Refers to the light nonmetals of periods II and III, B, C, N, O, Si, P, S. [7]
• Siegel B & Schieler L, 1964 Energetics of Propellant Chemistry, Wiley, p. 97: "…oxides and fluorides of the light metals Li, Be, Al, and Mg, and also of the light nonmetals B, C, and Si."
• Consultants Bureau Enterprises 1965, Kinetics and Catalysis, Volume 6, Consultants Bureau, p. 373: Gives IE for "light nonmetals" B, C, N, O, Si, P, S.
• Johnson RC 1966, Introductory descriptive chemistry of the nonmetals, W. A. Benjamin, p. 37: "The hydrides of the heavier nonmetals are gases at room temperature and are less stable than the hydrides of the light nonmetals."
• Goldschmidt 1967, Interstitial alloys, Elsevier, p. 43: Re selenium as a borderline interstitial compound former.
• Glasson, D.R. and Jayaweera, S.A.A. (1968), Formation and reactivity of nitrides I. Review and introduction. J. Appl. Chem., 18: 65-77: "The non-metallic components include light non-metals of the short periods (B, C, N, O, Si, P, S)." [54]
• Day RA & Johnson RC 1974, General chemistry, Prentice-Hall, p. 199: "Strength of bonds between H and nonmetals is greatest for the LM."
• Bowman A.L., Krikorian N.H. (1976) Interstitial Phases. In: Hannay N.B. (eds) Treatise on Solid State Chemistry. Springer, abstract: "The terms 'interstitial compound' and 'interstitial phase' are commonly applied to the compounds of the transition metals with the light nonmetals hydrogen, boron, carbon, nitrogen, and, sometimes, oxygen, silicon, phosphorus, and sulfur. The alternate term 'hard metals' has been used for the compounds with boron, carbon, nitrogen, and silicon."
• Williams RJP 1981, The Bakerian lecture 1981: Natural section of the chemical elements, Proc. R. Soc. Lond. B 1981 213, 361-397: "The light non-metals, H, C, N, O, P, S, Se…" [39]
• Fearn, D.R. and Loper, D.E., 1983. The evolution of an iron-poor core I. Constraints on the growth of the inner core. Gordon and Breach, London, p 351: "The core of the Earth is not composed of pure iron but contains a significant fraction of impurities, especially light non-metals [e.g. H, C, O, S, Si]."
• Bailar JC 1984, Chemistry, Academic Press, p. 942: "Although we commonly think of alloys as consisting only of metals, there are a few alloys that contain small proportions of light nonmetals, such as carbon, nitrogen, or boron."
• Norby, T. (1989). Hydrogen Defects in Inorganic Solids. Studies in Inorganic Chemistry, 101–142 (10): "In metallurgy, the presence and effects of light, non-metal elements are relatively well recognized and studied." [13]
• Vonsovskiĭ SV & Katsnelson MI 1989, Quantum Solid-state Physics, Springer-Verlag, p. 91: "Interstitial alloys are normally composed of metals and light nonmetals with small-sized atoms such as those of hydrogen, carbon, and nitrogen."
• Veith M 1990, Cage compounds with main-group metals, Chemical Reviews 1990 90 (1), 3-16: "In this review we discuss the chemistry, bonding, and structures of simple molecular cages that can be classified as heteroatomic and that incorporate besides the light nonmetals C, N, and O metallic main-group elements." [282]
• Williams RJP 1991, The chemical elements of life, J. Chem. Soc., Dalton Trans., 1991, 539-546(540): "These consequences follow directly from the acidity of light non-metal oxides in the Periodic Table, N, C, S and P." [13]
• Jenett, H., Bredendiek-Kämper, S. & Sunderkötter, J. Comparative plasma SNMS and AES measurements on ceramic powders and fibres. Mikrochim Acta 110, 13–22 (1993): "…the light nonmetals, which have high first ionization potentials…" [10]
• Alfassi ZB 1994, Determination of Trace Elements, Wiley, p. 301: "…the determination of light non-metals (H, C, N, Si, P, S)…"
• Williams RJP & Fraústo da Silva JJR 2005, The Chemistry of Evolution: The Development of our Ecosystem, Elsevier, p. 75: "Those formed by the light non-metals H, C, N, O are especially kinetically stable."
• Becker JS 2007, Inorganic Mass Spectrometry: Principles and Applications, Wiley, p. 261: "Both solid-state mass spectrometric techniques with high vacuum ion sources allow the determination of light non-metals such as C, N, O and P in steel."
• Hannay N 2012, Treatise on Solid State Chemistry: Volume 3 Crystalline and Noncrystalline Solids, Springer Science & Business Media, p. 253: LM form interstitial compounds with TM.
• Samsonov GV 2013, Properties Index: Issue 2 of Plenum Press handbooks of high-temperature materials, Springer, pp. 1-2: Light nonmetals = components of refractory compounds.
• Rodin AS, Carvalho A, Castro Neto AH 2014, Strain-Induced Gap Modification in Black Phosphorus, Phys. Rev. Lett. 112, p. 176801: "Despite the fact that the variety of truly two-dimensional (2D) materials has been increasing rapidly in recent years, graphene is set apart from the rest because it contains a single nonmetal atom type. In fact, the choices for such monotypic systems composed of light nonmetals are limited. Carbon is the only solid nonmetal in the second period of the periodic table. The third period contains two such elements: phosphorus and sulfur." [1,096] Qin et al. (2019) reported the production of large-size 2D selenium nano-sheets [69]; Liu et al. (2019) reported a theoretical study of the predicted stability of three stable 2D allotropes of selenium. [6]
• Timur A. Labutin, Sergey M. Zaytsev, Andrey M. Popov, and Nikita B. Zorov, 2014, Carbon determination in carbon-manganese steels under atmospheric conditions by Laser-Induced Breakdown Spectroscopy, Opt. Express 22, 22382-22387: "Atomic emission spectrometry is widely used in metallurgy laboratories due to the possibility of a rapid analysis of such light non-metals as C, Si, N, O, P, S." [23]
• Li at al. 2017, Influences of the adsorption of different elements on the electronic structures of a tin sulfide monolayer, Phys. Chem. Chem. Phys., 2017,19, 5423-5429: "Studies have shown that light nonmetal atoms [H, O] adsorption can induce the semi-metal graphene to become a semiconductor." [11]
• Ann-Christin Peter, Matthias Schnaubelt, and Michael Gente 2017, Multispectral X-ray imaging to distinguish among dental materials Imaging Sci Dent. 2017 47(4): 247-254: "Light non-metals: Elements with relatively low atomic numbers, including most soft organic materials." [1]
• Z. Wu, L. Zhu, Z. Zhang, Z. Jiang, F. Yang, Y. Wang, 2017, First principles study towards the influence of interstitial nitrogen on the hydrogen storage properties of the Mg₂Ni (0 1 0) surface, International Journal of Hydrogen Energy, Volume 42, Issue 39, p. 24869: "In recent years, the researches about doping light nonmetals (LNs) into Mg-based alloy and its hydride have been attracting more and more attentions. This is because that LNs have completely different doping mode (interstitial mode instead of substitutional mode) and comparatively high electronegativity compared with TMs." [2]
• Godovikov AA & Nenasheva SN 2019, Structural-Chemical Systematics of Minerals, 3rd ed., Springer, p. 9: "Light nonmetals found in intermetallic compounds. H, B, C, Si, N, P, Se, S, O."

Part 2

I'm not totally convinced because a significant number of these definitions include boron and silicon. That seems to tell me that while the term is relatively common, its precise composition is not. So, sorry, I still prefer "other". Hope you understand. ^_^ Double sharp (talk) 08:40, 29 September 2020 (UTC)[reply]

Table 2: NONMETAL PROPERTIES

Nonmetal	Ionisation energy (kJ/mol)	Electron affinity (eV)	Electro-negativity
Metalloids
B	897	27	2.04
Si	793	134	1.9
Ge	768	119	2.01
As	953	79	2.18
Sb	840	101	2.05
Te	879	190	2.1
Anonymous nonmetals
H	1,318	73	2.2
C	1,093	122	2.55
N	1,407	−0.07	3.04
P	1,018	72	2.19
S	1,006	200	2.58
Se	947	195	2.55
O	1,320	141	3.44
Halogen nonmetals
F	1,687	328	3.98
Cl	1,257	349	3.16
Br	1,146	324	2.96
I	1,015	295	2.66
Noble gases
He	2,372	−50	5.5
Ne	2,088	−120	4.84
Ar	1,521	−96	3.2
Kr	1,351	−60	2.94
Xe	1,170	−80	2.4
Rn	1,037	−70	2.06

@Double sharp: Well, that’s cool! I suggest we now have two “working” options(?). Or 2½ as I boldly suggest "pre-halogen nonmetals" is an apt neutral name, currently lacking any presence in the literature.

Here are some considerations that may ameliorate the small shortfall in your conviction quotient, re what seems to be the situation for light nonmetals. They encompass super-categories and the nature of boundaries; precision or a lack of it; interest dependance per Scerri; B and Si compared to the "other" light nonmetals; the imprecision of the other nonmetals category and the absence of writings on the collective chemistry of its members; and the classic situation all of this represents.

1. Super-categories. We have chosen to distinguish metalloids, from metals, and nonmetals, and to categorise boron and silicon as metalloids. In that context, while boron and silicon may display some of the properties of "light nonmetals", they are not "nonmetals".

2. The general nature of class boundaries. The boundary of a class is rarely sharp (Jones 2010, p. 170). The arbitrary boundary between metals and nonmetals is a classic example. Some other examples:

1. The alkali metal boundary is not sharp. Groups 2 (excl. beryllium) and 3, and many of the lanthanides and actinides, are "alkali" metals. Thus the approach of King (1995) who treats the lanthanides and actinides as main group elements. I recall you approvingly mentioning King.
2. The alkaline earth metal boundary is an overreach. Beryllium and magnesium are not alkaline earth metals. Thus, "Historically, beryllium and magnesium were not classed as alkaline earth metals, a convention which is followed here." (Parish 1997, p. 34: "The s-block metals", in The metallic elements).
3. Beryllium is more like a post-transition metal or metalloid than an alkaline earth metal.
4. We categorise lanthanum and actinium as a lanthanide and actinide respectively yet they are transition metals.
5. The early actinides behave like transition metals.
6. Silver is categorised as a transition metal (and it does have a few such properties) yet its chemistry is predominately that of a main-group or post-transition metal (Rayner-Canham 2018).
7. We show group 12 as post-transition metals yet they are about as commonly regarded as transition metals.
8. Carbon, arsenic, antimony, and bismuth are electronically semi-metals, yet we categorise carbon as nonmetal, arsenic and antimony as metalloids, and bismuth as a post-transtion metal.
9. Depending on the context, antimony may be alt-categorised as a post-transition metal, as you have properly explained. (See item 4, below.)
10. Polonium is relatively commonly categorised as a metalloid yet we categorise it as a post-transition metal.
11. We categorise xenon and radon as noble gases (nonmetals), yet they are both "reactive" nonmetals. Indeed, radon has been reported to form a cation in aqueous solution. (I acknowledge your previous explanation as to the distinction between reactive non-noble nonmetals and reactive noble gases.)
12. Early on in our periodic table article we say, "Placing elements into categories and subcategories based just on shared properties is imperfect. There is a large disparity of properties within each category, with notable overlaps at the boundaries, as is the case with most classification schemes." We further discuss category overlaps in the same article: Linking or bridging groups.
13. In our nonmetal article, we say: "The distinction between categories is not absolute. Boundary overlaps, including with the metalloids, occur as outlying elements in each category show or begin to show less-distinct, hybrid-like, or atypical properties."

3. Our own categories lack precision. Aside from the AM; the AEM (with a caveat); the halogen nonmetals, and the noble gases, our other categories naturally lack precision. There is a little duplication here with item #2 above but I wanted to bring out this observation as an under-appreciated feature of (i) our scheme, and (ii) such schemes and category names generally, as per the COPTIC literature-based database.

3a. Imprecision is endemic in the composition of categories spanning groups 10 to 16. Consider there are at least five competing proposals for which elements to include in the post-transition metals category: the three most common contain six, ten and thirteen elements, respectively. For the nonmetals, aside from the halogen nonmetals and the noble gases, consider the nine schemes and fourteen category names set out in our article.

4. Context is it. The most important thing, in my view, is the context for the categorisation decision. If that is made clear, then scientists (and readers) need not lose sleep over the hard cases, as Jones says. For example, we need to make clear why we categorise:

• lanthanum and actinium as a lanthanide and an actinide, rather than as transition metals;
• why we currently show the composition of group 3 they way we do;
• group 12 as post-transition metals, rather than transition metals; and
• astatine as a post-transition metal, rather than as a metalloid, or a halogen nonmetal.

5. Interest dependence. Picking up on the theme from #4, Eric Scerri (2020, p. 13) observed that, "…whatever kinds are being considered, there is always a certain degree of interest dependence that enters the stipulation of sets of entities be they tigers, galaxies or elements." In this case I suggest the interest dependence is the terminology used within the literature, combined with the frequent occurrence, and pragmatic acceptance of, blurriness or boundary overlaps, in the context of the discipline of classification science, and periodic table colour categories. Citing Jones (p. 171) once more:

"Scientists should not lose sleep over the hard cases. As long as a classification system is beneficial to economy of description, to structuring knowledge and to our understanding, and hard cases constitute a small minority, then keep it. If the system becomes less than useful, then scrap it, and replace it with a system based on different shared characteristics."

6. Shared characteristics. In this case, I suggest these are those shown in Table 1. While boron and silicon show some properties associated with light nonmetals, they are horses of a rather different colour.

7. The imprecision of the other nonmetal faux-category. Hydrogen is not always included, as is the case with selenium. Sometimes one (boron) or two (boron and silicon) other elements are counted as other nonmetals. (Going by memory).

8. Other nonmetals have no accessible collective chemistry. It is possible to read about the collective chemistry of the light nonmetals. It isn't possible to do so, from what I have seen and can recall, for the collective chemistry of the so-called other nonmetals. The latter is no surprise given the clueless nature of the term "other" nonmetals.

9. What is before us is the classic situation of a part of the periodic table in which there is neither a standard category name nor complete agreement on the elements appropriately classified as such. We can however address these shortcomings based on about a dozen attributes most consistently found in the literature, as I have posted here, and the presence of a relatively common category name, acknowledging some marginal shifting of the boundaries, depending on the author.

In conclusion, perfection (100% unanimity in precision) is the enemy of good. For the light nonmetals, the acceptability threshold is well met, being anchored in the literature, and having a contextual basis exemplified by our decisions on the boundaries of the lanthanides and actinides (15 elements each rather than 14); and the composition of the post-transition metal category, and that of the metalloid category. Sandbh (talk) 07:14, 30 September 2020 (UTC)[reply]

Part 3

@Sandbh: To me, though, the situations are a bit different. Ln and An with 15 elements each is IUPAC-recommended; metalloids at least are taken here to include only the six that are almost always there (not Po and At which are not there half the time); post-transition metals at least can be rationalised by the name in one way. What exactly is a "light" nonmetal? Speaking just as the name, helium seems pretty light too, so does fluorine. Yes, I agree we have this issue with "alkali metals": Mg-Ra, Sc-Lr, Ln and An, probably Rf are also "alkali". The difference is that "alkali metal" is a standard term and no one analyses it, so no one will probably complain about the imprecision inherent in the name. Is "light nonmetal" quite standard enough that people won't analyse it? Or will it give the mistaken impression that helium is not light or is not a nonmetal? Besides, "light" also makes me think of why I don't like "reactive nonmetal". Light compared to what? Selenium has been called a heavy metal, after all.

Yes, there is such a thing as context. But do we have the time in the lede to explain the context? And is it the right place to do so? If not, then I think it may be better to stick with a faux-category that is easier to explain, rather than a real category that requires some contextual explanation. But I don't want to sink the improvement of cutting up the nonmetals category just because I'm not comfortable with this. Double sharp (talk) 09:22, 30 September 2020 (UTC)[reply]

@Sandbh: Striking the last sentence, sorry. I still feel bad about possibly sinking the improvement, but ultimately I feel that "light nonmetal" is not better than "reactive nonmetal". Perhaps even worse because while at least "reactive nonmetal" gives me the correct impression that the remaining ones are, well, not reactive (they're exactly the noble gases), "light nonmetal" gives me the incorrect impression that things like helium and fluorine and neon are not light, whereas they are. So, my apologies, but I think I have to withhold my support for the nonmetal change unless it's "other". There is neither a standard category name nor complete agreement on the boundaries, as you say; so we should reflect that for now. If we seek to change that, well and good, but the bandwagon must start outside WP, and a standard name has to emerge. Then we can change it. Just like the group 3 issue: I accept that we can't show -Lu-Lr at the present moment because it's not currently the most common form. So, really sorry about this, but I think I can't quite get over my concern about the "light nonmetal" name. Double sharp (talk) 17:35, 30 September 2020 (UTC)[reply]

@Double sharp: That's OK. I saw your earlier, now redacted, post indicating provisional support for light nonmetals provided "other" fails to gain more support.

I was very pleased seeing that you were willing to change your mind (as you’ve done in other matters; and as I did when I switched back and forth on group 3; and in other matters). As well, prompted by your question about what are "light" nonmetals, I discovered last night there was more to the story. I intend to post that shortly. The tremendous thing is you've indicated you will not withdraw support if it's other nonmetals and that we’ve come a long way in understanding what’s going on in this part of the periodic table.

Really, to me, I guess you’ve just changed your position slightly to support other nonmetals, presumably unless light nonmetals gets more support, rather than supporting light nonmetals provided "other" fails to get more support. When I look at it that way, I'm not sure you've really changed your position ^_^ Sandbh (talk) 22:54, 30 September 2020 (UTC)[reply]

Part 4

@Double sharp:

There are three parts to this contribution:

I.	Brief summary of the background to the term "light nonmetals"
II.	Observations and conclusion
III.	More reference-extracts from the literature

There is a lot to consider here.

I. A brief summary of the background to the term "light nonmetals"

It was known from an early time (West 1931) that metals formed interstitial compounds with some "light metalloids". Nonmetals in those days were called metalloids. That was before the term "metalloid" came to be confined to the elements along the p-block diagonal.

In those days: (a) it was known that the halogens did not form such compounds; and (b) noble gases were not regarded as nonmetals—they were regarded as forming their own super-category (more on this to follow), along with the metals; and the metalloids i.e. nonmetals.

For (a), that is consistent with Vargel (2004), who treats the halogens separately from the noble gases, and the metalloids, which is what he calls the rest of the nonmetals. Glasson and Jayaweera (1968) are relevant too, with their comments about refractory compounds being formed only with "light non-metals" (a term which they used earlier) having a not too high EN, hence once again ruling the halogens out of consideration.

In the case of the noble gases not being regarded as nonmetals that is a practice that continued up until at least 2005[!], at least in New York State, on the basis that NG don't accept electrons.

From Medical and surgical therapy (1918) and Freeman and Keller (1984), we know antimony, tellurium and iodine were regarded as heavy metalloids or nonmetals i.e period 5+. That is consistent with Williams (1981), and Godovikov and Nenasheva (2019) referring to selenium, in period 4, as a light nonmetal. Of course, selenium has been regarded as a heavy metal in another sense. That's nothing of any consequence. Selenium does not meet the 5 g/cm³ cut-off. Cf., what happened with the categorisation of astatine: Immediately following its production in 1940, early investigators considered it a metal. In 1949 it was called the most noble (difficult to reduce) nonmetal as well as being a relatively noble (difficult to oxidize) metal. In 1950, astatine was described as a halogen and (therefore) a reactive nonmetal. In 2013, on the basis of relativistic modelling, astatine was predicted to be a monatomic metal, with a face-centred cubic crystalline structure. We used to colour astatine as a metalloid!

On the metalloids, the old practice of this being a term for nonmetals fell out of favour with the rise of the semiconducting industry in the late 1950s and early 60s. It came to be confined to the semiconducting elements boron, silicon, germanium, and tellurium, and arsenic and antimony too, since they also existed in semiconducting forms. Relevant too are Glasson and Jayaweera (1968) who refer to carbides, nitrides, sulphides, and phosphides of boron and silicon, but not borides or silicides of carbon, nitrogen, sulfur and phosphorus.

Going back again to the earliest days, there were "light" metalloids, being the nonmetals as we call them, now in periods 1 to 4 i.e. period 1= hydrogen; 2 = boron, carbon, nitrogen, oxygen, fluorine; 3 = silicon, phosphorous, sulfur, chlorine; 4 = arsenic, selenium, bromine. Recall germanium was thought to be a metal.

Technically, fluorine, chlorine, and bromine were light metalloids or light nonmetals but that was a distinction in name rather than substance. They did not form interstitial or refractory compounds and were not studied in that context. Rather, halogen chemistry was already so distinctive compared to the other nonmetals that it become its own area of study.

So, the many intersecting and overlapping historical threads eventually coalesce out into the following categories:

• the noble gases, which were never historically regarded as nonmetals in the first place;
• the halogens, with their own long-standing brand of distinctive chemistry, dating back to Berzelius;
• the metalloids proper, with the establishment and rise of the semiconductor industry, and perhaps presaged by Pauling in 1947 with the publication of his classic and influential text book, "General chemistry: An introduction to descriptive chemistry and modern chemical theory". He described the metalloids as 'elements…occupy[ing] a diagonal region [on the periodic table], which includes boron, silicon, germanium, arsenic, antimony, tellurium, and polonium'; and
• the "light nonmetals" proper, with their (a) capacity to form interstitial or refractory compounds; and (b) various biogenic and life-forming (or destroying, in the case of nerve gases, and explosives) qualities.

Recall the 1968 reference by Glasson and Jayaweera to the presence of transition metal energy levels in compounds of the alkaline-earth metals with nonmetals. The sitation is thus:

• transition metals proper: Groups 3−11
• honorary transition metals: Ca−Ra
• faux transition metals: heavy p-block metals.

For the light nonmetals the sitation is somewhat analogous:

• light nonmetals proper: H, C, N, O, P, S, Se
• honorary light nonmetals: B, Si, (Ge)
• "light nonmetals" in a quite narrow sense: F, Cl, Br; He, Ne, Ar.

II. Observations and conclusion

1. The historical background to the term "light nonmetal" is representative of the iterative, emergent and overlapping nature of chemistry. Among other things, this contributes to the idiosyncrasies seen in chemistry; we’ve discussed lots of these.
2. The collective properties of interest are set out in the literature.
3. A “bandwagon" is already there.
4. "Light nonmetal" has a relatively common meaning and boundary, anchored in multiple fields of material science, acknowledging some blurriness at the edges (cf., transition metal; post-transition metal; metalloid)
5. "Light" is the main source of energy for all living organisms; a rough estimate of the composition of the biosphere is C₁₄₅₀H₃₀₀₀O₁₄₅₀N₁₅P₁S₁Se_0.5 (Jørgensen & Mitsch 1983, p. 59; Brooks 1992, p. 4) cf., our seven biogeochemical cycle articles, one for each light nonmetal.
6. In another sense, “light” has a meaning of the early members of a set, as in the light lanthanides or actinides. The light nonmetals could thus be alt-regarded as the nonmetals occurring in the earlier groups (1, 14−16) rather than the last two groups (17−18).
7. "Other" struggles to merit or sustain a distinctive colour; "light" means something, in two to three senses.
8. After colour-categorising the alkali metals; alkaline earth nonmetals; transition metals; lanthanides; actinides; post-transition metals; metalloids; halogen nonmetals; and noble gases, we are left with a set of nonmetals more commonly recognised, for better or for worse, as light nonmetals.
9. That fluorine, chlorine, bromine, helium, neon and argon, in a quite narrow sense, are light nonmetals doesn’t override their categorisation as halogen nonmetals (c. 1825) and noble gases (1898) respectively. Equally, that most of the rare earths and heavy actinides are alkaline earth metals doesn’t necessarily clash with their categorisation as either transition metals, lanthanides, or actinides. In all cases, the categorisation is based on collective attributes of interest rather than a single cross-category attribute.
10. Heavy metals is a related category with a more common meaning, and a boundary (density ≥ 5 g/cm³) with some blurriness at the edges e.g. (1) the inclusion of the metalloids arsenic and antimony, and the putative “light nonmetal” selenium (4.81 g/cm³, as noted), and (2) whether or not to count the radioactive and synthetic metals (e.g. polonium, astatine). Despite being a somewhat arbitrary category—noting we don’t use it—it retains its utility.
11. We colour code hydrogen as a reactive nonmetal. If so, why is it on the other side of the periodic table, separated from the rest of the reactive nonmetals by some 15 groups, rather than over, say, fluorine? That would place it adjacent to helium. Of course we made our decision here based on the literature which supports such a wide separation, never mind it looks so odd. (Bent was especially critical of the H-He gap).
12. We colour code aluminium as a post-transition metal even though this is ambiguous. It is a PTM in terms of its location post-group-12; it isn't in the fact that aluminium has zero d electrons, unlike all other post-transition metals. Despite this confusion, we make our categorisation decision.
13. Polonium appears in nearly half of metalloids lists, yet we colour it as a PTM despite it being adjacent to the zigzag line. What happened here? We made a categorisation decision.
14. The "other nonmetals" are sometimes simply categorised as "nonmetals" alongside the halogen and noble gas categories. That does not mean that e.g. F–I are not nonmetals. Rather, it means they have sufficiently special properties to warrant being given a superseding names (as eventually happened with B and Si). Thus while F and He are light nonmetals in a technical sense, they have sufficiently special properties to warrant being allocated to the superseding categories of halogen and noble gas, respectively. Not to mention they lack the key properties of special interest associated with the light nonmetals proper.
15. We seem to have a proclivity for needlessly holding ourselves to higher standard than is found in the literature. Consequently we knock ourselves out striving for categorisation perfection when Jones says scientists need not lose over the hard cases as long as these constitute a minority (and the categorisation scheme provides an economy of description, and is useful to structuring knowledge and our understanding).
16. Our classification science decisions in the vicinity of groups 11−17 are the outcome of various intersecting and overlapping categories, as seen in the literature, each of which share more in common than they don't. "Light nonmetals" is no different.
17. We may wish scientists had not associated e.g. the AEM name with Be and Mg, or e.g. the pnictogens name with P−Bi, but they did and we have to run with it. Hydrogen, fluorine, chlorine, and the noble gases are pnictogens too! Ditto, the scientists who become interested in unraveling the mysteries of refractory and interstitial compounds formed by TMs with the light nonmetals proper could've suggested a more focused category name. But they stuck with light nonmetals, given (a) the absence of the characteristic properties of interest in the halogens and noble gases (the latter then not regarded as nonmetals); and (b) that the group 17 and 18 elements had their own more interesting properties that had earned them separate, headline category names, and we have to run with it.
18. As an encyclopedia, we have an obligation to reflect the literature, regardless of whether we like or dislike the suitability or clarity of its terminology. True, light nonmetals is not an IUPAC-endorsed category. That said, while the periodic table remains the organising icon of chemistry, it's been borrowed, adapted, tailored and presented in various different guises including by the physicists, geologists, astronomers and others. And if light nonmetals happens to be the most popular (relatively speaking) category of sufficient rigour, which other nonmetals isn't, then there it is. Same thing happened with the metalloid category and IUPAC's recommendations against its use in 1953, '59 and '71, which were widely ignored.
19. The nearest analogy I can think for all of this is passing all the elements through a series of sieves (akin to the Sieve of Eratosthenes). After the dust settles downs, all that is left are light nonmetals.
20. We do the best we can with extant category names (based on inclusive shared attributes plural, rather than no attributes in the case of other nonmetals) unless a more meritorious or popular category name appears in the literature.

Pragmatically, the merits of light nonmetals, in the context of our classification science approach, appear to confer frontrunner status on same unless other nonmetals is somehow shown to be demonstrably better.

This conclusion seems to be effectively the same as what you said pre-redaction i.e. provisional support for light nonmetals provided "other" fails to gain more support.

Please let me know if you have any o/s concerns. Sandbh (talk) 00:55, 4 October 2020 (UTC)[reply]

III: Supplementary extracts: light nonmetals; lighter nonmetals; light metalloids; lighter metalloids; heavy metalloids

• Transactions of the Albany Institute 1872, vol. 7, p 303: "With a genial temperature ranging between 40° and 130°, when the waters ceased simmering, and the lighter metalloid elements oxygen, hydrogen, nitrogen, chlorine, carbon, sulphur, phosphorus, sodium, potassium, etc . subsided into…" Comment: Is the reference to sodium and potassium as lighter metalloids elements are hangover from Erman and Simon's (1808) suggestion for using the term metalloid to refer to the newly discovered elements sodium and potassium?

• Eclectic, The Magazine of Foreign Literature, Science, and Art, 1887, p. 313: "…the next layer consists mainly of water, composing the ocean; within that comes a stratum of not very solid rock, principally built up of the lighter metals, aluminium, calcium, magnesium, and so forth, combined with the lighter metalloids, oxygen, silicon, and carbon, in more or less loose and spongy compounds.

• Medical and surgical therapy v. 5, 1918, p. 118: "Heavy metalloids (iodine, etc.) or metals (zinc, iron , etc.) and their derivatives which are used for dressing."

• Bardet J, Crook WJ 1931, Atlas of arc spectra: analytical tables for spectrochemical studies, p. 10: "In most cases, with a little practice an observer can determine the components of a mixture in about a quarter of an hour, even if the mixture is complex. Naturally some exception must be made in the case of the light metalloids which do not give arc spectra."

• West CJ 1931, A Survey of American Chemistry, National Research Council (U.S.). Division of Chemistry and Chemical Technology, p. 121: "The study of the structure of compounds of metals and light metalloids may in time throw light on the nature of intermetallic compounds in general, which often have extremely complicated structures, for the existence of which no explanation has so far been suggested."

• Journal of Inorganic Chemistry, 1958, Volume 3, Issues 4-6, p. 1: "compounds between the transition group of metals and the light metalloids."

• French Science News, 1962, p. 175: "The following subjects are dealt with: alloys of alkaline metals or alkaline earth metals with a metalloid; alloys of refractory transition metals with a light metalloid; alloys of alkaline metals and alkaline earth metals with each other."

• Encyclopedia of Science and Technology 1966, McGraw-Hill, p. 479: The transition metals form a novel group of binary compounds with the lighter nonmetals, boron, carbon, nitrogen, and, to a limited extent, oxygen. These substances exhibit metallic luster and conductance."

• Proceedings of the Symposium on Structure and Properties of of Amorphous Metals, 1978: "…of light metalloid elements of group MA , IVA and VA (B, C, Si, Ge and P). These small metalloid atoms are supposed to occupy relatively larger holes in the dense random packing structure of the metal atoms, transferring electrons to the unfilled d holes of the transition metals."

• Soviet Physics: Solid state, 1979, vol. 20, p. 1773: "In interstitial solid solutions, we have small atoms of light metalloids (H, O, C, N ) which become distributed in interstices of a metal lattice."

• Cabri LJ 1981, Platinum-group Elements: Mineralogy, Geology, Recovery, p. 11: "For example , Pd forms metallic PdAsS with two of the lighter nonmetals and Ru avoids forming a metallic structure even with the heavy metalloids in RuSbTe."

• Freeman AJ, Keller C 1984, Handbook on the Physics and Chemistry of the Actinides, p. 75: "The decrease is more regular, and the minimum less marked, for heavy metalloids (Te, Sb) than for light metalloids."

• Cotton & Wilkinson 1988, Advanced Inorganic Chemistry, p. 188‎‎: "... the boranes , from the simplest B2H6 to the most complex , together with the number of electrons available , do not permit of structures or bonding schemes like those for hydrocarbons or other “ normal ” compounds of the lighter nonmetals.

• Doklady: Physical chemistry 1989, vol. 301-303, p. 1040: The attempts to replace some of the oxygen atoms by other lighter metalloids are most interesting , since the presence…or absence…of superconductivity in this system is related specifically to the oxygen sublattice.

• Manahan SE 2002, Toxicological Chemistry and Biochemistry, 3rd ed., p. 235: "In Chapter 10 elements were discussed that as a rule tend to be toxic in their various forms (As, O and ozone, P; F, Cl, Br, I; Rn, Ra), Chapter 11 covers toxic inorganic compounds of elements that not themselves generally regard as toxic. These elements include for the most part the lighter nonmetals located in the upper right of the periodic table ( Figure 1.3 ) and exclude the heavy metals . Most of the elements involved in the inorganic compounds discussed in this chapter are are those that are essential for life processes. Any division between "toxic" and "nontoxic" elements is by nature artificial in that most of the heavy metals have compounds of relatively low toxicity, and there are deadly compounds that contain elements essential for life; p. 211: "The noble gases, only some of which form a limited number of very unstable chemical compounds of no toxicological significance…

• Jean JYC, ‎Peter E Mallon, ‎D M Schrader 2003, Principles And Applications Of Positron And Positronium, p. 30: "Positron binding is common among one- and two-electron atoms, except for the heaviest few (Helium is included in the noble gas group, not two-electron atoms, in this chapter). Positronium binding seems to be common for the alkali metals and halogens, plus some of the lighter nonmetals (C and O) and coinage metals (Cu).’

• Vargel C 2004, Corrosion of Aluminium, Elsevier, p. 357: "Oxides of light metalloids are gaseous under standard temperature and pressure conditions, such as the oxides of carbon and nitrogen. Oxides of the heavier metalloids are normally solids; this is the case of silica, SiO₂, and phosphoric anhydride P₂O₅, but with the exception of sulphur dioxide SO₂, which is gaseous. [this author distinguishes between metals, metalloids (inc. As, Sb), halogens (F to I) and noble gases."

• Williams RJP, J.J.R Fraústo da Silva 2005, The Chemistry of Evolution: The Development of our Ecosystem, P. 168: "The very different kinetic properties allow a variety of activities of H, C, N, O quite different from those of S and P in compounds, and together they are the only available lighter non-metals of functional value, except trace Se, for the above function (but see uses of halogens late in evolution)."

• N. Atanassov, M. Manolova, R. Rashkov & A. Zielonka 2007, Influence of boric acid and Mn on electrolytic deposition of Co from low concentration sulphamate electrolytes, Transactions of the IMF, 85:2, 94-98: "transition metals may alloy with light metalloids (H, C, N)."

• Wells AF 2012, Structural inorganic chemistry, p. 1294: "There is another kind of solid phase, the interstitial solid solution, in which the small atoms of some of the lighter non-metals occupy the interstices between the atoms in metal structures."

---

• Glasson & Jayaweera 1968, as cited previously:

"These materials form one of three fundamental classes of refractory compounds:

1) compounds of metals with non-metals, such as borides, carbides, nitrides, oxides, silicides, phosphides and sulphides;

2) compounds of non-metals with each other, such as carbides, nitrides, sulphides and phosphides of boron and silicon, and also alloys of B and Si.

3) compounds of metals with each other, known as inter- metallic compounds.

The character of the chemical bond between the components of these compounds is mainly metallic or covalent with a small proportion of ionic bond.

These types of bond are established mainly by transition metals with non-metals having ionisation potentials sufficiently low to avoid exclusive ionic bond formation; they are also formed between two non-metals and certain metals with each other.

The non-metallic components include light non-metals of the short periods (B, C, N, O, Si, P, S). The chemical bond in the lattices of these compounds (in addition to the s- and p-electrons of the metallic and non-metallic components respectively) is formed also by the electrons of the deeper incomplete d- and f-levels of the transition metals.

Isolated atoms of metals of the odd subgroup of group 11, the alkaline-earth metals, do not have any electrons in the d- and f-shells, but in compounds with non-metals, energy states corresponding to these shells may occur."

Other references

• Brooks R.R.: Noble metals and biological systems: Their role in medicine, mineral exploration, and the environment. Routledge, Roca Baton (1992)
• Erman and Simon (1808) "3. Dritter Bericht des Hrn. Prof. Erman und des Geh. Oberbauraths Simon über ihre gemeinschaftlichen Versuche" (Third report of Prof. Erman and State Architect Simon on their joint experiments), Annalen der Physik, vol. 28, no. 3, pp. 347-367
• Jørgensen SE & Mitsch WJ (eds), Application of ecological modelling in environmental management, part A, Elsevier Science Publishing, Amsterdam (1983)

It would be helpful if someone inserted {{unsigned}} above. YBG (talk) 01:50, 5 October 2020 (UTC)[reply]

Comments

@

WT:CHEM, what "light nonmetal" would mean to them, and see if the term is commonly understood with your meaning by seeing if they'd mentally think it excludes helium and fluorine? If most of them do understand it that way, then I'll be convinced to support. But if that's not the case, then my preference list remains "other/halogen/noble gas" > "reactive/noble gas" > "light/halogen/noble gas". Double sharp (talk) 19:23, 4 October 2020 (UTC)[reply

]

@R8R, YBG, ComplexRational, and DePiep: Firing pings (context being my post immediately above). Double sharp (talk) 19:45, 4 October 2020 (UTC)[reply]

I can't imagine a universe in which a class called "light nonmetals" excluded helium, the 2nd lightest nonmetal.. YBG (talk) 01:59, 5 October 2020 (UTC)[reply]

@YBG: Thanks. My initial thoughts are that we categorise He as a noble gas, rather than as a light nonmetal. In the same way, we categorise La as a Ln. I cannot imagine a universe in which a class called transition metals excluded La (not electronically, anyway). Or a universe in which a class called AEM excludes most of the rare earths, and the late An, as these two sets behave like AE metals yet we include Be and Mg as AEM, yet neither of them are AE metals. I cannot imagine calling e.g. N, O, F, P, S, Cl, Br, and Ne-Xe metals, yet that is what astronomers do. More later. Sandbh (talk) 13:19, 5 October 2020 (UTC)[reply]

@Sandbh: I am not suggesting that He belongs in this collection of elements, merely suggesting that since He does not belong with them, the term "light nonmetals" seems to be problematic. YBG (talk) 18:40, 5 October 2020 (UTC)[reply]

Same happens with the light lanthanides, even though they are heavy metals. Sandbh (talk) 13:25, 5 October 2020 (UTC)[reply]

@Double sharp: Thank you. Asking other folks has merit. As I posted under "Astronomy" I feel we need to stress-test LM a bit more. Sandbh (talk) 00:22, 6 October 2020 (UTC)[reply]

@YBG: I suggest there are nomenclature problems all over the periodic table. For example, I see periodic tables showing "nonmetals", "halogens", and "noble gases". Such tables suggest to me that halogens and noble gases are not "nonmetals". Ontologically, anything not a "metal", is a "non"-metal. Yet I regularly see periodic tables showing metals-metalloids-nonmetals. Are metalloids thus not non-metals, in these depictions? Are the metalloids boron and silicon not light nonmetals? What is a transition metal? That remains an area of terminological uncertainty. I only raise these questions to suggest such nomenclature "problems" are relatively common. They arise due to the haphazard and diverse way science develops and the immaturity of classification science. As I see it, our purpose is to be reflective of the state of the literature rather than making judgements about (and effectively obfuscating) its problems, or its lack of consistency. Of course, if there are such problems we can discuss them in the relevant article, as we do.

It seems to me that we can ask ourselves, "Per the literature, after the noble gases, and the halogen nonmetals, what it is the most common term used to refer to the remaining nonmetals?" Light nonmetals. Is this an ideal term? No it is not, but there it is. The literature is what it is. As you rightly said, it does not mean that He, a noble gas, is not a light nonmetal. Sandbh (talk) 00:22, 6 October 2020 (UTC)[reply]

@Sandbh: The problem is that your quotes don't convince me that the literature is what you think it is. Where are the standard textbooks in the fields you cite as support using this term, as Smokefoot would probably ask, rather than isolated articles? Why are some of your quotes about "light metalloids", "lighter nonmetals", "heavy metalloids" rather than "light nonmetals"? Where is the clear definition that "light nonmetals" is being used in a sense that excludes metalloids, halogens and noble gases (as it stands it's plausible in many of your sources that "light nonmetals" extends wider than whatever elements are listed and just some examples happen to be given?). If it were truly a standard term, shouldn't you have no problems finding any of these, that would deal with my concerns? Double sharp (talk) 18:39, 7 October 2020 (UTC)[reply]

@Double sharp: That's fine. I suspect this is a case of what I wrote before:

"… a proclivity for needlessly holding ourselves to higher standard than is found in the literature. Consequently we knock ourselves out striving for categorisation perfection when Jones [a PhD emeritus professor of science himself], says scientists need not lose over the hard cases as long as these constitute a minority (and the categorisation scheme provides an economy of description, and is useful to structuring knowledge and our understanding)."

I ack your objection to Jones. As noted, the principle of what he's saying is universal.

So, there are no textbooks on post-transition metals. Even what relatively few references there are to post-transition metals vary in their boundaries. The last book on metalloids appeared in 1966, 54 years ago! Yet we show PTM and metalloids as sharp categories. My quotes about "light metalloids", "lighter nonmetals", and "heavy metalloids" served to illustrate that a distinction between light and heavy elements has a long history. Similarly, there are light and heavy Ln, and light and heavy An. As well, there are light TM and heavy TM. The former distinctions are left-right; the latter period 4, and periods 5-6. Thus, light nonmetals are in groups 1, 14-16; the vertical cut off is between groups 16/17. The horizontal cut off is period 4/5. Just as there in no standard definition of TM, PTM or metalloids, there is no standard definition of light nonmetal. Pragmatically, I suggest we have to make do with what we can find in the literature rather than looking for the unattainable. Sandbh (talk) 05:52, 8 October 2020 (UTC)[reply]

Astronomy

@Sandbh: But the astronomers are using their own definition of "metal". Which is not the chemical definition of metals. For sure, each discipline has the right to use its own terminology within its sphere of inquiry. And if we're talking about astronomy, we should indeed call anything but H and He a "metal". But this is going to be a general table for use on chemistry-related articles. And I don't think you're going to find any chemists using the astronomical terminology when they're talking about chemistry. Which is why my question is simply: since this is an entry-level chemistry article, shouldn't we stick to terms that any contemporary chemist would understand in the sense we're using them? And I'm not convinced that "light nonmetal" in a sense that excludes He is among them.

If I were writing for myself, I might not actually use the names "alkali metal" and "alkaline earth metal" precisely because of this problem. I would probably just use terms like "group Is metals", "group IIs metals" (in my group numbering scheme where Is = 1 and IIs = 2), and sometimes "heavier group IIs metals" for Ca-Ra (sometimes including Mg maybe). And then maybe speaking instead if I wanted to be more general of the class-A metals that give generally basic oxides, saying that Li-Fr and Ca-Ra are among the most extreme of the bunch. But that doesn't mean I can or should change it on WP because the category names AM and AEM are so common and even IUPAC-approved. Moreover I wouldn't think that using "heavier group IIs metals" really creates a clear new category there rather than just meaning exactly what it says: modifying "group IIs metals" by picking out the ones that are, well, heavier. And I suspect that "light nonmetal" is in precisely the same situation. Same situation with "light lanthanide": La is light for a lanthanide even if among metals it's one of the heavier ones.

And if I were writing for myself, then yes, for me La is not a transition metal, but an inner transition metal. Even electronically. That's because of 4f involvement in La. (The s block metals from the fourth period onwards for me might be called honorary transition metals.) That precisely follows what happens if you take one IUPAC definition of "inner transition element" (f-block) and "transition element" (d-block) while advocating Sc-Y-Lu, so it's definitely an imaginable universe even if it's not the one we are in right now. One of Jensen's papers gets very close to that (putting La in an "Inner-Transition Block", whereas Sc, Y, and Lu are in a "Transition Block"). The fact that in this sense "inner transition element" is not a subset of "transition element" should not be a problem; a dwarf planet is not a planet and a skew field is not a field.

This sort of thing, combined with the insidious tendency of any oft-repeated phrase in English to sound like it is a term, is precisely why I don't want to create anything that sounds like a generally used term if it is not already one. I'd rather have "other nonmetals", to be honest. The "other" is an effective inoculation against thinking that it's a real term, IMHO; it clearly reflects that there currently isn't a generally-used term outside perhaps individual chemistry branches for these elements as a whole; and it even fits what I've said earlier. Which is that such categories seem to me to always have been intended to just group together similar elements of interest, with no real expectation that they manage to cover the whole periodic table, never mind cover each element once and once only. Trying to use only common categories thus, as I see it, will almost inevitably lead to a few leftovers. I think we should admit that with "other nonmetals". If one sees it as a problem (I don't personally, but maybe you do), then I think one would have to draw attention to it outside WP first so that a term one advocates (here, I guess, "light nonmetal") becomes commonly understood parlance for all chemists in the meaning that one wants for it. Once we get into that situation, then surely I'll support. I'm just not convinced we are in it already (though I could be if it turns out that many introductory texts use the term in a meaning clearly defined to exclude the halogens and noble gases, and it just happens to not be in the texts I read). Double sharp (talk) 16:59, 5 October 2020 (UTC)[reply]

---

@Double sharp, YBG, and R8R: Yes, I like "other nonmetals" and would like to fully stress-test "light nonmetals" before relegating it.

1. I suggest our PT article is an entry-level "periodic table" article, and NOT an entry-level chemistry article. While the PT has its roots in chemistry, Eric recently said that, "The periodic table has now become as much the property of physicists, geologists, astronomers and others as it is of its chemical originators." (2020b, p. 7)

2. In this context, the views of the chemists—while they merit consideration—don't necessarily have primacy. That is another reason why it won't matter if we merge AM and AEM.

3. In the absence of a suitable IUPAC term, and since 'light nonmetals' is found in the multiple contexts of:

x-ray imaging

, I suggest it has primacy in this part of the periodic table.

4. We have applied the same approach to the absence of IUPAC terminology for post-transition metal; and metalloid, since IUPAC does not "own" the periodic table. Sandbh (talk) 23:49, 5 October 2020 (UTC)[reply]

I suggest the key consideration is letting go of the PT = chemistry paradigm, per Eric. I didn't get this for a long time. I got it after researching the multi-disciplined use of "light nonmetals" in the literature. Sandbh (talk) 23:49, 5 October 2020 (UTC)[reply]

---

@Sandbh: But that's still precisely the point. Like it or not – it seems most chemists still think the PT is their jurisdiction. Enough that Scerri wrote an article about the "tyranny of the chemist". Yes, especially for the superheavies there's already been complaints about IUPAC (and not IUPAP) unfairly dominating the process when clearly the physicists are the ones with the more relevant expertise here. But just look at the presentation I linked, where Alan Astbury is quoted as saying "For historical reasons the Chemists cling to this process dearly". There you have it; like it or not, chemists de facto have primary status, with the only strong challenge coming from physicists, and we should therefore reflect that IMHO. I ask, which projects have added banners to Talk:Periodic table? Just us; the chemistry project; and the physics project. Where are the geologists and astronomers?

You are correct that the PT is relevant to pretty much every field of chemistry and other fields besides. But chemistry de facto has primacy and it is not hard to see why. What do geologists use it for, for example? Probably for geochemistry which demands knowledge of the chemical properties of the elements anyway. Maybe the only strong challenge comes from physics – but that seems to be only in the sense in which physics explains chemistry (the electronic bases of the PT are at the intersection of physics and chemistry). The squabble over the superheavies is only about gatekeeping which elements are recognised as discovered, not about their chemical properties; but it would be just as correct inscribing the elements into a simple rollcall ("hydrogen, helium, lithium, beryllium, ...") as on a table.

Which is why I ask: is "light nonmetal" a term that only practitioners of some fields and subfields will recognise? Or is it something that almost all will, or has official status, or at least is such that most people would be able to guess its meaning correctly without prior knowledge? If it's the second, then I'm for it. But so far, the responses here don't make me confident that it is that. Double sharp (talk) 10:53, 6 October 2020 (UTC)[reply]

@Double sharp: Well, the tyranny of the chemist Eric refers to is that which occurs within the chemistry community. That’s all. It doesn’t refer to periodic tables per se and references to same nor to categories of chemical elements mentioned across multiple disciplines.

Which WP projects attach an interest to the WP periodic table article has no relevance in terms of the literature. WP cannot cite WP, so to speak.

For the geologists, there is the Earth Scientist’s periodic table. For the metallurgists, Faith Habashi had a go. There is an astronomer’s table here. Stowe’s physicists table (La-Ac) is here etc

Light nonmetals is used in at least the twenty fields I posted earlier. Most people would be able to guess its meaning (e.g. hydrogen, oxygen) without prior knowledge, unlike AM, AEM, TM, Ln, An, PTM, metalloid, and halogen. Quite a few non-specialists would wonder why helium was coloured as a noble gas rather than a light nonmetal. Since the lede is supposed to pique curiosity that’s fine. The explanation would be in the categories section. Sandbh (talk) 10:37, 7 October 2020 (UTC)[reply]

@Sandbh: Sure, those tables exist, but exactly who uses them? When geologists refer to the periodic table, are they more likely to refer to the "Earth Scientist's periodic table", or simply follow what the chemists do? Considering that the paper introducing an Earth Scientist's periodic table outright calls the usual table "conventional", and the general conservativeness of scientific literature, I strongly suspect you will not see those alternative tables around. My limited experience of physics texts, at least, strongly suggests a preponderance of chemically normal arrangements, nothing like Stowe's table. Like this from Cassidy et al.'s Understanding Physics (incidentally, Sc-Y-Lu). Can you find any standard textbooks at all for those fields that, instead of the standard chemistry forms (18-column, 32-column, Sc-Y-La, Sc-Y-Lu, Sc-Y-*), use one of these rearrangements?

I am perfectly aware that what WP projects tag the Periodic table article is not a statement in the literature. Nonetheless it is indicative of interest.

Most people would not guess the meaning you want to give "light nonmetals" correctly, at least if the reactions here are anything to go by. They would mostly wonder why helium and/or fluorine was not considered among the light nonmetals. Sure, you can explain it all you like, but I don't see any sign that "light nonmetal" is commonly used in the meaning you want to attach to it. But, we can ask

WP:CHEM to be sure. Double sharp (talk) 18:38, 7 October 2020 (UTC)[reply

]

Yes, agree, not commonly used. That said, it is the most common term used, across multiple academic disciplines, for the nonmetals in question. We do not get to choose which names are suitable or not. We do not get to "censor" the periodic table on the basis that e.g. some people might not get it, or that chemists might raise some concerns, whereas some solid-state materials scientists would yawn. In the best encyclopaedic tradition, we report what is in the literature. Anything else is non-encyclopaedic. The classification science approach of the chemists, in this part of the table (groups 11 to 16), is a shambles, in any event. As I see it, YMMV, we are stressing out for no reason with any basis in science on the ground.

I would seek input from WP:RFC. And yes, it'd be a good to sound out some e.g. scientists in the 20 academic fields in which the term has been used. The chemists, through their own neglect, have very little to contribute here, as I see it. I did sound out CHEMED-L about "light nonmetals", and received a nil response. They don't care. Sandbh (talk) 06:16, 8 October 2020 (UTC)[reply]

Halogen nonmetals

I personally think of "light nonmetals" as of C, N, O, and F, and maybe P and S. Selenium is sometimes referred to as a heavy metal, so I'd find it strange to have our table call it a light nonmetal.

@Double sharp: I'm sorry, I haven't been following the discussion lately. I'd like to ask you a question but maybe you've already answered it (if so, I couldn't find the response). Do you not find it problematic that we are going to have "halogen nonmetals," therefore using the term "halogen" and at the same time excluding astatine from the halogen category? I'm somewhat hesitant about this because "halogen nonmetal" sounds like tautology to me but then I force myself to remember there is astatine, and I think that this is too much thinking for such a simple thing, but one the other hand, we get to feature the word "halogen." I'd appreciate a genuine opinion.--R8R (talk) 18:58, 5 October 2020 (UTC)[reply]

@R8R: My general opinion of it was really that I don't seem to find a consensus in the English-language literature on whether "halogen" implies "nonmetal" or not. Sometimes it seems to mean the whole group. IUPAC 2005 Red Book excludes tennessine, it is true, but only because in 2005 it wasn't even discovered let alone acknowledged. But in 2016 we got from IUPAC the recommendation for naming new elements that said "it was apparently not anticipated that the pace of discoveries of new heavy elements would soon lead to new elements of the halogen and the noble gas groups". So here "halogen" clearly means the group and includes Ts. (Yes, this is how we got "tennessine" and "oganesson". I'm still not happy about it for elements that look more like gallium and germanium or tin.) But it seems that for some people "halogen" implies some properties that exclude the element being a metal, so you will see titles written by chemists like "Astatine: Halogen or Metal?". So, a mess. If you remember Fricke's papers on predicted properties of the superheavies, it rather entertainingly presents the problem. He writes in the tables "halogen" for the chemical group of element 117. But on the next page in the text he writes "Element 117 (eka-astatine) is expected to have little similarity to what one usually calls a halogen, mainly because its electron affinity will be very small". Same thing going on with element 118, where he writes in the tables "noble gas", but he also puts it in scare quotes on p. 120, and writes on p. 106 "This effect is expected to occur, even from a chemical point of view, together with the large spin-orbit splitting effect at the end of the 7p elements at 118, where a noble gas element is actually located but a very reactive element with an easily obtainable 4+ state would be expected because the last four 7p_3/2 electrons are so loosely bound."

If I was writing my own book, I'd say "a pox on this", clearly say that "halogen" and "noble gas" are categories of similar elements and not including the whole group, proceed to complain about Ts and Og getting the -ine and -on suffixes, and point out that even people who put hydrogen in group 1 are not moved to call it an alkali metal. (Although I kind of suspect that doubts about that are why sometimes you see it pulled out of there, as if chemical properties rather than electronic structure fixed element placement; one need only look at the very strong secondary relationships in groups II and III to understand why that's not the case, as well as the laughably lame relationship of N to Bi that no one questions. Sorry, it's just annoying to me. ^_^) But, I'm not writing my own book, I'm discussing what WP should show, and I have to deal with how the situation in the English-language literature seems to be bad. To me "halogen nonmetal" seems to be the best way to do it. If, like me, you think "halogen" already implies "nonmetal", then it's just a tautology, but not wrong. And if, like some people seem to, you think "halogen" only implies "group 17", then "nonmetal" becomes a necessary indicator to get rid of At and Ts. (Don't let's get into the problem that "halogen" means "salt-former" and things like N, O, P, and S form salts too. Words mean whatever they mean regardless of where they come from!) Yes, I worry that it has a danger of making it seem like "halogen nonmetal" is a term in itself, because any two-word phrase repeated enough in English starts sounding kind of like an actual technical term. But, frankly, I see it as a problem inherent in the literature that prevents us from getting a good categorisation. If IUPAC ever gets around not only to giving us an answer on group 3, but also an actual definition of what a metal is, plus a slightly better version of the difference between a category and a group, then we can fix it. Or indeed if it somehow gets standard in the literature without IUPAC projects pushing it along. Although in that case, I would suggest doing what I do at User:Double sharp/Periodic Table and colour only by block and metallicity, and not try to make the categories cover every element once and once only; they were never meant for that, they were only there to group similar elements together, so it's unsurprising that when you try to make them cover every element once and once only they don't manage to do it.

Maybe the situation in the Russian-language literature is better. I recall Droog Andrey called At an ambiguous member of the halogen family in Archive 34. But (1) you and he definitely would know better than I, and (2) maybe this is more of a matter for the Russian Wikipedia than the English one. Usage might differ nationally (although I don't think they should, the fact is that they do). Remember: for one thing, Polish Wikipedia has a definitely stronger case for Sc-Y-Lu than we do, because while for us it's a bunch of people complaining against the establishment who haven't become dominant yet (even though they still seem to win in terms of pure numbers of people arguing, they haven't convinced the majority who aren't arguing either because they silently like La, silently don't care, or legitimately don't know there's an argument at all; I dislike that situation but that's how it is for now), Sc-Y-Lu made the actual Polish establishment (link is to the PWN encyclopedia). So, while I'd like to hear that it's not so bad in Russian literature, I am not sure how well that argument will work at convincing others. Double sharp (talk) 21:43, 5 October 2020 (UTC)[reply]

Suggestion re notes

Could the group 3 and 12 notes be perhaps incorporated into our periodic table templates like {{

Compact periodic table}}? Since these are IUPAC things they would seem to be worth a line like that. Polish Wikipedia

already does something similar with group 3 and period 8. (OK, Polish Wikipedia takes Sc-Y-Lu as default and footnotes the possibility of Sc-Y-La, but it's the same idea and we can do it the other way round.) It also improves accuracy by noting that the heavy group 3 elements, whatever you think they are, have dual citizenship in the TM category in our current arrangement (IUPAC says transition elements are groups 3-12 or maybe 3-11, after all). That's something that is currently missing.

(Of course, for the extended tables such a note also makes sense for period 8 saying that what we show is just one of many possibilities. Or perhaps we should in fact stop period 8 at element 138 on the grounds that that's as far as everyone more or less agrees: Seaborg, Fricke, Pyykkö, Nefedov, Kulsha, mimicking the Polish Wikipedia idea. Then the note would say that the appearance of period 8 beyond element 138 is under scientific debate. And of course the note on -La-Ac vs -Lu-Lr would become a note on -La-Ac-121 vs -Lu-Lr, since if memory serves Fricke shows Sc-Y-La-Ac-121. See also The Physics Hypertextbook for other inspiration for that idea.)

Such a thing would, in my opinion, not be giving undue weight to these issues given their high-level acknowledgement (you can't ask for anything higher). And it would certainly be as neutral as something can be while IUPAC is still deliberating on one of them. Perhaps we can also frivolously note that it also would make me happy as a partisan of the side we don't take on both issues, which possibly suggests that it succeeds at being neutral. (^_-)-☆ Double sharp (talk) 23:36, 27 September 2020 (UTC)[reply]

+1 Sandbh (talk) 04:04, 28 September 2020 (UTC)[reply]

Latest iteration

@Double sharp, R8R, YBG, ComplexRational, and DePiep: I have posted this to our periodic table article. It duplicates our current scheme. The legend only has two notes re IUPAC matters, as suggested by Double sharp.

DePiep: If you have any concerns please raise them here rather then reverting. Thank you. Sandbh (talk) 03:14, 4 October 2020 (UTC) Sandbh (talk) 03:14, 4 October 2020 (UTC)[reply]

Well, this contribution has not even been considered. But sure keep expecting old-fashionied talkpage behaviour. -DePiep (talk) 19:41, 4 October 2020 (UTC)[reply]

Alkali metal color

I have decided to join the fun of making bold changes and softened the color of alkali metals. It is now this:   (see sodium for an example). I don't think there's going to be any controversy but I thought I'd let you all know just in case. Nobody liked that old aggressive red anyway.--R8R (talk) 14:59, 26 September 2020 (UTC)[reply]

Like Double sharp (talk) 16:39, 26 September 2020 (UTC)[reply]

That's #ff9d9d then. #ff9d9d. Would be nicer if you had published it. Still a mess, really. -DePiep (talk) 21:17, 26 September 2020 (UTC)[reply]

The problem is, R8R, and it shows clearly: there are too many reds in the category legend. Your change makes AE red similar to transition metals red. -DePiep (talk) 21:21, 26 September 2020 (UTC)[reply]

I reverted. Please, grow up and behave. -DePiep (talk) 21:35, 26 September 2020 (UTC)[reply]

@DePiep: I'll see you at WP:ANI. Sandbh (talk) 23:28, 26 September 2020 (UTC)[reply]

I reverted DePiep's revert. @DePiep: You are not the arbiter of what does or does not work. Sandbh (talk) 05:03, 27 September 2020 (UTC)[reply]

What about my argument? -DePiep (talk) 08:47, 27 September 2020 (UTC)[reply]

First, they stand apart, and you told me yourself a while ago that it is okay to have similar colors if they stand apart. Second, I don't see how one could conflate these colors anyway. Third, it is only natural that whatever argument you have is diluted by "request" to another editor to "grow up and behave" after they make an uncontroversial action, and it may be a good idea to remember in the future if you wish to have your arguments heard (I carefully distinguish between "thinking you're right" and "having others agree with you").--R8R (talk) 09:46, 27 September 2020 (UTC)[reply]

1. "a while ago" is quite out of context. Please speak for yourself, and don't pull quotes as an argument or proof. For example, you could have written: "but you said ...?" (note the "?") 2. Maybe you don't see, but you could be open for people who point to this. There are four (four) similar reds now. Let's not call

wp:access selectively. 3. You edited Bold, I did R and D. I see no problem with that? -DePiep (talk) 19:54, 27 September 2020 (UTC)[reply

]

Sure. I'm not going to look up for that quote (I think both of us are in agreement that it would be a waste of time), so yes, let's discuss the matter anew. I am open to people who point to this, but "open" does not mean "accepting what they say without any questions." There are two major concerns: one, I still don't see the problem; there is neither verifiable proof (such as calculated color difference) nor subjective proof ("they are too similar to distinguish for me"). Two, my belief is that we agree that the current color scheme is bad, and changing one color would not improve it dramatically in any event but there is at least some hospitability in this project for a softer red for the time being.--R8R (talk) 06:16, 29 September 2020 (UTC)[reply]

As you have read elsewhere, I have no problems with BRD here. I kindly ask you not bring up the argument that you know to be incorrect. What problem I do have is discussed elsewhere.--R8R (talk) 06:20, 29 September 2020 (UTC)[reply]

"I kindly ask you not bring up the argument that you know to be incorrect."??? Please clarify,

WP:PA. -DePiep (talk) 14:33, 2 October 2020 (UTC)[reply

]

@DePiep: I actually didn't say that off the bat for two reasons: one, I did not think that the editors here wanted to hear about our squabble outside of this project (this place is meant to hold discussions about articles, templates, and other encyclopedic stuff and what supplements it), and two, what I was referring to had occurred merely a few hours before you wrote that message, so my understanding of it was that you remembered what I was talking about. But since you're asking me to clarify what I was referring to, I will of course do so (though I am somewhat puzzled as for why you chose to do this: my understanding is that the story doesn't make a good impression of your actions).

There was an ANI a few days ago, in which a complaint against you was filed. I participated in that ANI, too. Here is a relevant quote (all quotes in this paragraph use original formatting): "I didn't expect this to be a controversial action: other editors called for that previously, and even DePiep themselves had said changing the old color was "good choice for access reasons" just a few hours before I made that change. In response, I got three consecutive messages from DePiep: in the first one, I was told that it "would be nicer if you had published it" (I will refer to this later), in the second, a problem was identified, and in the third one, I was told to grow up and behave (I did not make any edits concerning this issue between those messages)." In response to my own contribution, you said, "you turn such regular BRD steps into some constructed nasty attitude you try to smear me with." I said to this, "Yes, there is nothing wrong with noting what you think is a problem; that's fine, simple BRD is fine. That's not the takeaway from my mention of it. A normal BRD cycle doesn't result in telling another editor to "grow up and behave," that's the uncivil behavior here." This is an important quote. I wrote that message on September 27, at 14:07 UTC. You responded at 14:47, which means you had read my response by then. And then, five hours later, at 19:54, you write in this very section, "You edited Bold, I did R and D. I see no problem with that?" You did know that the problem I identified wasn't the BRD cycle, it was the language you used. And yet, you acted as if BRD was a problem I identified. In theory, there could be a chance you misread me (I did misread you once very recently, and I have yet to write about it). In all honesty though, did you?

I generally try to watch what words I say. In the last couple of weeks, I have not used the phrase "personal attack" to describe your words against me, even though I could back up such a claim. That was on purpose, and that is because I believe that actions speak louder than words and because I believe my argument to be strong enough not to require such inflation. I have, in fact, not used the word "lie" here either. That was on purpose, too. There is not a single word in that post that was factually incorrect and which you purposely presented otherwise. I know that and I didn't use the word "lie" to describe it. However, from reading your post, one could easily conclude that you were puzzled how the straightforward BRD was a problem, and from what I mentioned in the previous paragraph, that can't be (unless you fail to read what I write carefully). That was why I referred to your words as to an incorrect argument. I don't know whether you did that on purpose (which is why I didn't use the word "lie"), but I do know that what you said resulted in an incorrect argument (which is why I used the words "argument" and "incorrect").--R8R (talk) 16:12, 3 October 2020 (UTC)[reply]

Before I seriously process this post: is it content-aimed or other? -DePiep (talk) 19:54, 4 October 2020 (UTC)[reply]

I am surprised to see you use my words against me and then claim you had not processed them.

It is a response to your accusation that I conducted a personal attack against you by claiming you had lied that you twice made at

WP:ANI (1, 2). It is saddening to me to see that you made the second accusation after I explained in detail how that was not the case, and it is especially saddening given that you didn't even process my reply before making such a claim the second time.--R8R (talk) 08:28, 5 October 2020 (UTC)[reply

]

Can we please trademark the term "group"

A few recent posts here used the term "group" in an apparently generic sense. I found this somewhat confusing and very distracting. May I suggest that we agree here at

WP:ELEM

1. Only use the term group to refer to group (periodic table)
2. Only use the term category to refer to our colored metallicity categories, past present and proposed.
3. Use the terms set or collection to refer to other names for sets of chemical elements.

I am finding it hard to isolate the posts on my phone. I think they were from R8R and Double sharp, but I could be mistaken. I would appreciate it if you would go back and edit these posts to read "group collection" (my preference) or "group set". Thank you. YBG (talk) 17:31, 26 September 2020 (UTC)[reply]

@YBG: I can't find such a generic use of "group" in my posts here. Could you point it out? So far I've used "category" to mean "any possible set of relatively homogeneous chemical elements", with the idea that there are more categories than the ones we actually use. That's close to how I'd talk about this externally. The issue I was discussing is whether "halogen" and "noble gas" and similar things are really category names or group names: from what I have seen of the situation, I would externally advocate them as only category names, but the nature of the distinction and whether or not there is a distinction seems really not clear in the English-language literature. Double sharp (talk) 18:11, 26 September 2020 (UTC)[reply]

re YBG: strange question. "group" is defined well in PT world: a PT column. We cannot change that. "category" is informal, used as such in enwiki only. "set" is the great way to note any combination of elementsd one want s to list. -DePiep (talk) 21:27, 26 September 2020 (UTC)[reply]

The lede and what goes in it

@YBG and Double sharp: You've each expressed concern about the lede as a high level summary v the notes in the PT image.

WP guidance on images in the lede says:

"As with all images, but particularly the lead, the image used should be relevant and technically well-produced. It is also common for the lead image to be representative because it provides a visual association for the topic, and allow readers to quickly assess if they have arrived at the right page. Image captions are part of the article text."

The PT in the main body of our article shows (1) the name of the element in full; (2) Z; (3) the element's symbol; (4) atomic weight; (5) state of matter; (6) a colour legend; (7) names for six of the groups; and (8) notes dealing with state of matter conditions, and standard atomic weight.

The proposed image removes (1), (4), (5), (7), and the notes. It retains (2), (3) and (6) and a few notes of its own. That seems like a suitably high overview, without simplifying things too much. --- Sandbh (talk) 00:05, 27 September 2020 (UTC)[reply]

Perhaps now superseded by V4. Sandbh (talk) 04:32, 27 September 2020 (UTC)[reply]

Incivil behaviour by User:DePiep

Here. Sandbh (talk) 07:24, 27 September 2020 (UTC)[reply]

... and this is the closure: /Archive. -DePiep (talk) 20:47, 11 October 2020 (UTC)[reply]

Understanding the uniqueness of the 2p‐elements in the periodic table

Open access. Heavy on the maths. --- Sandbh (talk) 00:12, 29 September 2020 (UTC)[reply]

Although the qualitative understanding is relatively straightforward (see Kaupp's older paper). Double sharp (talk) 08:45, 29 September 2020 (UTC)[reply]

Five things we still don’t know about water

1. How many kinds of ice are there?* (at least 17)
2. Are there two kinds of liquid water?
3. How does water evaporate?
4. Is the surface of liquid water acidic or basic? (acidic apparently)
5. Is nano-confined water different?

* "The remarkable variety of crystalline ice forms results from the tetrahedral network of strong hydrogen bonds formed among neighboring water molecules. In the condensed phases of water, each molecule optimizes its hydrogen bonding capacity by forming four hydrogen bonds at near-tetrahedral angles. The hydrogen bonds inside Ice I_h form an open, three-dimensional structure with a low density."

The article is here. It's a subscription magazine but says you get two free views. Sandbh (talk) 00:21, 29 September 2020 (UTC)[reply]

"Categories", and even their "color", over PT essence

This edit, detailing that neither enwiki's coloring nor enwiki's categorisation is that important over groups, periods, blocks in the PT, says enough. Here Sandbh undoes the statement. Enough. Sandbh does not

OWN the PT. -DePiep (talk) 23:58, 2 October 2020 (UTC)[reply

]

Hi Sandbh. You keep changing FA Periodic table and its supporting features without crisp support. That is not acceptible. If you keep editing and behaving this way, I will have you blocked. -DePiep (talk) 00:12, 3 October 2020 (UTC)[reply]

Are you fine? -DePiep (talk) 00:14, 3 October 2020 (UTC)[reply]

@DePiep: I am tremendous, than you for asking. Are you OK? You seem to have gotten yourself into a pickle as a result of what is occurring at WP:ANI.

You too, do not

WP:OWN

anything.

I have changed the PT article a few times, following discussions here at WP:ELEM. There is no up front requirement to obtain consensus. The few comments for the first edit attracted suggestions and comments. There was no dissent. You reverted anyway.

The other edits I made concerning categories etc were followed by four editors who corrected some typos, and nothing else. Anyone of them could have changed my edits but chose not to. So five editors, including me, raised no concerns by their actions. As a fellow WP:ELEM member, you chose to effectively undo my work, without discussion. Of course, you are entitled to that but it does not, in my view, contribute to harmonious relationships within our project.

When you threaten to block me in circumstances where I make good faith edits, usually in the context of discussions here, I get rather upset. When you say that you will have me blocked when you have no intrinsic power to have me blocked, I get further upset. I would prefer you to raise your concerns here rather than threatening me or citing "no consensus obtained", when no such consensus needed to be obtained in the first place. Sandbh (talk) 07:25, 3 October 2020 (UTC)[reply]

---

On the order of categories, groups, block etc, I think I will follow chronological order:

• Metals, metalloids, nonmetals: The recognition of metals and nonmetals was around before the periodic table.
• Categories: These were around before the periodic table e.g. Berzelius and the halogens (~1825)
• Next would come groups and periods, per DIM circa 1869+
• Then would come blocks, which seem to date from the time of Janet (1928?)

--- Sandbh (talk) 07:35, 3 October 2020 (UTC)[reply]

@Sandbh: And there's the rub: historically these things were discovered back-to-front, because the more fundamental things require deeper and deeper drilling down. Mostly I suspect electronic structure and hence blocks, groups, and periods get explained before the periodic table is actually shown, because the former explain the latter. Then the trends, including the metal-to-nonmetal one, can be explained. Double sharp (talk) 11:31, 6 October 2020 (UTC)[reply]

A resonating abecedarian approach to the 18-column periodic table

​​​​​I'm posting this in the context of our discussions re group 3, and related group configurations like He over Be.

Periodicity is approximate, not precise. Accordingly there is no fundamental requirement for each space in the periodic table to be occupied by just one element. Blurring is not prohibited.

The "non-problems" go away if groups 2 and 12 resonate between (i) Be-Mg-Ca-Sr-Ba-Ra; (ii) Be-Mg-Zn-Cd-Hg-Cn; (iii) He-Be-Mg-Ca-Sr-Ba-Ra; (iv) He-Be-Mg-Zn-Cd-Hg-Cn; and (v) Zn-Cd-Hg-Cn. This means group 18, too, is a resonator between (i) He-Ne-Ar-Kr-Xe-Rn and (ii) Ne-Ar-Kr-Xe-Rn.

Likewise, groups 3 and 13 resonate between (i) Sc-Y-La-Ac; (ii) Sc-Y-Gd-Cm; (iii) Sc-Y-Lu-Lr; (iv) B-Al-Ga-In-Tl; (v) H-B-Al-Ga-In-Tl; (vi) B-Al-Sc-Y-La-Ac; (vii) B-Al-Sc-Y-Gd-Cm; (viii) B-Al-Sc-Y-Lu-Lr; (ix) H-B-Al-Sc-Y-La-Ac; (x) H-B-Al-Sc-Y-Gd-Cm; and (xi) H-B-Al-Sc-Y-Lu-Lr.

H resonates across groups 1, 13, 14, and 17.

For the remaining ten groups, "one element one space" is a good enough approximation.

So there it is: eight groups (1-3; 12-14; 17-18) resonating, with twenty-four possible configurations; and ten fixed group (4-11; 15-16).

From the list below:

• IUPAC is type HK;
• Lu in group 3 is type K;
• He-Be and group 3 as -Lu-Lr is type EK;
• Jensen preferred a type CDK;
• Pauling’s EN table is type N* (the * denotes an irregularity, since H is assigned to no group)

The most common table has all eight defaults.

The various resonances are like shadows on the wall in Plato’s cave. A nuanced understanding of the periodic table, and its variants, is appreciated by keeping this resonating abecedarian approach in mind.

THE 24 RESONANCES

Group 1 (2)
[A] H-Li-Na-K-Rb-Cs-Fr (default)
[B] Li-Na-K-Rb-Cs-Fr

Group 2/12 (5)
[C] Be-Mg-Ca-Sr-Ba-Ra (default)
[D] Be-Mg-Zn-Cd-Hg-Cn

[E] He-Be-Mg-Ca-Sr-Ba-Ra
[F] He-Be-Mg-Zn-Cd-Hg-Cn

[G] Zn-Cd-Hg-Cn (default)

Group 3/13 (11)
[H] Sc-Y-La-Ac (default)
[J] Sc-Y-Gd-Cm
[K] Sc-Y-Lu-Lr

[L] B-Al-Ga-In-Tl (default)
[M] H-B-Al-Ga-In-Tl

[N] B-Al-Sc-Y-La-Ac
[P] B-Al-Sc-Y-Gd-Cm
[Q] B-Al-Sc-Y-Lu-Lr

[R] H-B-Al-Sc-Y-La-Ac
[S] H-B-Al-Sc-Y-Gd-Cm
[T] H-B-Al-Sc-Y-Lu-Lr

Group 14 (2)
[U] C-Si-Ge-Sn-Pb (default)
[V] H-C-Si-Ge-Sn-Pb

Group 17 (2)
[W] F-Cl-Br-I (default)
[X] H-F-Cl-Br-I

Group 18 (2)
[Y] He-Ne-Ar-Kr-Xe-Rn (default)
[Z] Ne-Ar-Kr-Xe-Rn

On this basis, the IUPAC table is fine, acknowledging they don't give sufficient context. In that sense it isn’t fine. Sandbh (talk) 06:02, 4 October 2020 (UTC)[reply]

Droog Andrey's 32-column table

@Sandbh: Yes, almost all of these are part of the paradigm of secondary and tertiary relationships (see these two papers of Jensen.)

However, I think it's not restricted to the groups you're talking about. C-Si-Ti is briefly discussed by Greenwood and Earnshaw while they talk about the group 4 trends, and Mendeleev's table by being 8-column also shows such as it mixes the A and B groups: therefore, the elements appearing in group VI on his table are O, S, and then Cr, Se, Mo, Te, and so on. (Secondary relationship from S to Cr is well visible in maximum oxidation state; consider sulfate vs chromate.) This is equally what Rayner-Canham calls the Group (n) and Group (n + 10) linkage.

So, I feel that all these are additional "resonances" that are needed for a nuanced understanding. So the following is how I would deal with the issue. It's similar to what I've talked about on your talk page, though I go a bit more at length here since this is explicitly about the secondary relationships. Actually, a lot more at length. Sorry; there's a TL;DR at the end.

We can easily draw as Droog Andrey did the significantly useful ones:

For me, yes, blurring is prohibited, and periodicity is precise. To understand periodicity, in my opinion, we have to clearly define the bases. An element is defined by its atomic number and the structure of its electronic cloud. The first everyone agrees on, I hope; the second is less obvious, but I think we'll agree that it's important, because without it we would have no reason why the period lengths should be as they are and not something else. Note that I do not mean the chemically irrelevant ground-state gas-phase or condensed-phase configurations, but the set and total occupancy of the orbitals that can be involved in chemical bonding. For the d and f block elements, the first two, while standard, are really simply sweating the small stuff.

The periods come from the requirement that Z increase; the groups, from periodic recurrence of analogous outer electronic clouds. And the period break at the noble gases (and indeed their inertness in itself) comes from the large energy gap between np and (n+1)s subshells. Ergo, everything is fixed and precise. The place of an element on the periodic table, for me, is a direct reflexion of its innermost nature: its atomic number and its electronic structure (whence its block).

For example, consider, lutetium. Its position is successively fixed in this approach as follows. Firstly, having Z = 71, it must come between ytterbium (Z = 70) and hafnium (Z = 72) on the table. Then, having valence electronic shell structure (5d 6s 6p)³, it belongs in the d block (because it uses inner d orbitals but not inner f or g orbitals), and it belongs with other d block elements with analogously three valence electrons: scandium with (3d 4s 4p)³, yttrium with (4d 5s 5p)³, and lawrencium with (6d 7s 7p)³. Lanthanum, having instead the valence electronic shell structure (4f 5d 6s 6p)³, doesn't belong with them. If we allow La to stand there with the different shell structure, then questions will arise about aluminium (3s 3p)³ which also has chemical similarities, and that way lies either overcomplication or inconsistency in my view. If we repeat this for all elements, we fix everybody's position. (Regarding how this handles the problem of group 2, with magnesium (3s 3p)², calcium (3d 4s 4p)², and zinc (3d 4s 4p)¹² resulting in no true higher homologue, we deal with this s block problem later.) So, I say: because of the importance of valence structure (it is behind what to a first approximation is 100% of chemistry humans deal with), in all contexts we should have Sc-Y-Lu shown as it is the primary relationship. However: lanthanum is also related to Sc and Y, because it likewise has three valence electrons. That's a kind of secondary relationship. And I also say that, because this also comes from the valence structure, in all contexts we should have Sc-Y-La also kept in mind as a secondary relationship. And exactly the same thing with aluminium, which we showed already. So, my viewpoint is: don't take any one thing and say "this is for this context, that is for that context, etc.", because all of them are valid for every context. We just need to know which ones are primary and which ones are secondary or tertiary.

Secondary and tertiary relationships can simply be explained separately. They are relationships between two elements which have the same number of valence electrons but are not in the same group. And tertiary relationships are relationships between two elements which have the same number of valence vacancies but are not in the same group. In general primary relationships are strongest, followed by secondary, followed by tertiary, but it's not a hard-and-fast rule (helium has no primary relationships, but its tertiary relationship is stronger than its secondary one). Because for group membership you need the analogous outer shell structure. So the general rule is that groups follow primary relationships whenever possible, and secondary relationships if there are no primary relationships (the latter situation only affects the s block).

While I strongly feel it is inconsistent to take Sc-Y-La alone (because any argument strong enough to do that, if applied elsewhere, tends to result in either Be-Mg-Zn, B-Al-Sc, or pulling Th out of the f block as well); as part of a unified, holistic conception of secondary and tertiary relationships, as just another colourful addition to the periodicity in the set {H-F-Cl, He-Ne-Ar, B-Al-Sc, Sc-Y-La, C-Si-Ti, Ti-Zr-Ce, N-P-V, V-Nb-Pr-Pa, O-S-Cr, Cr-Mo-(Nd)-U, F-Cl-Mn, Ca-Sr-Yb, Be-Mg-Zn}, I feel that it is perfectly correct and useful. For me, individual tables that take out one secondary or tertiary relationship and ignore all the others are harmful in how they make it seem like those are above the others; but a table that recognises them all is perfectly sound.

Some secondary or tertiary relationships will be strong, some will be weak, some will be essentially nonexistent, but that's all right; knowing which ones are more useful is a matter of chemical intuition. Primary relationships (the ones in the same group) can just as well be strong (Na-K), weak (Sn-Pb), or in extreme cases essentially nonexistent outside extreme conditions (He-Be, N-Bi, Ne-Og). But chemistry has never stopped us from putting Og in group VIIIp; that was never the basis. You deduce chemistry painstakingly, one step at a time, from the electronic structure which is the basis, not the other way round. There can also be relativistic secondary and tertiary relationships which occur when you get a pseudo-noble-gas configuration like Hg, Cn, or Fl; whence relationships like the "knight's move" ones, or things like At-Nh or Rn-Cn or Si-Og.

H over C might at a stretch be taken as an extra relationship, as both are half-filled. It is not a very strong relationship, but that's all right, there are weak ones at every class. There are a bunch of elements that end up being chemically similar without a real secondary or tertiary relationship, like Al and Fe. I'd create a class of quaternary relationships for these catch-alls. Diagonal relationships can also fit here, as they are basically the result of mutual cancellation of greater atomic size and greater atomic charge for polarising power (Li-Mg, Be-Al, B-Si being the most famous ones). Strong quaternary relationships might at least match valence (Al to Fe, Y to Gd); weak ones might not (H to C, diagonal relationships); but they all exist and are useful to keep in mind.

Here we have united most of Rayner-Canham's extra relationships under a single paradigm. I consider that a better approached to a nuanced understanding because of its power at generalisation. Now, without having to add more letters, we can immediately guess that period 8 is going to cause another split with secondary relationships of the first few superactinides to the early actinides, with the real homologues coming later. Predictive power is needed, not just descriptive power, in my opinion. To me, we should be able to say something as a prediction for the 8th period elements that should be just around the corner (hopefully I haven't jinxed it).

Notably, this partly explains why the group 3 dispute tends to go back and forth. Sc-Y-La and Sc-Y-Lu are both valid relationships of some kind. The problem is that if you only look at chemical and physical properties, you cannot distinguish between a primary and a secondary relationship; they can both be pretty strong. So a partisan of Sc-Y-Lu can note that a lot of properties fit, and say that when Sc-Y-La fits it is just an extra relationship; and a partisan of Sc-Y-La can note that a lot of properties fit, and say that Sc-Y-Lu only fits because of the lanthanide contraction. In order to decide, I consider it necessary to do what Jensen pointed out in 2017, and look at the fundamental property of electronic cloud structure. He even outright mentions "the necessity of looking not only at ground-state configurations but at available low-lying empty orbitals as well", which is very much resonant with what DA and I have been saying. The only problem is that that argument only works if you accept the bases above. I surely do, and consider these bases to be clearly important because they reflect the valence structure that controls chemistry. But if you don't agree that that's the most important thing, then this is hardly going to convince. In which case the whole thing keeps going.

Now I finally explain the s block. Calcium has some kind of d involvement and isn't a true-blue 100% homologue of magnesium, but zinc also has some kind of d involvement. So there is no primary relationship and we pick the secondary one (Ca) over the tertiary one (Zn). The weird smoothness of the group 1 and 2 trends makes sense under this paradigm because they are actually partly secondary-relationship trends: they match things like B-Al-Sc-Y-La-Ac and C-Si-Ti-Zr-Ce-Th which are analogous to Be-Mg-Ca-Sr-Ba-Ra and Li-Na-K-Rb-Cs-Fr. But there isn't a true analogy of any possible group 1 or 2 trend to B-Al-Ga-In-Tl-Nh and C-Si-Ge-Sn-Pb-Fl, so we pick these secondary relationship trends because there is nothing better.

Similarly, the same thing happens for the superheavy elements: the standard relationships stop working because of early drowning of 7s and 7p_1/2. But, the result is close enough. Oganesson still has 7s² 7p⁶ outside even if 7s is not really contributing and neither is 7p_1/2. In some sense it is like helium over beryllium: in both cases we have s², but the meaning of that s² changes. As the whole idea of the np-to-(n+1)s energy gap is based on the non-relativistic part of the periodic table, it seems OK to me to treat the late relativistic corrections as a perturbation of the basic structure. So we can idealise the s subshells as still being there even if they really are not. This is however still not quite a secondary relationship, because the valence electron counts don't match; rather it's more of a pseudo-primary relationship (what would have been a primary relationship if relativity hadn't spoiled it).

My preferred group numberings attempt to echo the secondary relationships: so for me, B-Al-Ga-In-Tl-Nh are group IIIp, which are clearly related to Sc-Y-Lu-Lr as group IIId and La-Ac as group IIIf. (Element 121 would start a group IIIg.) The s block groups, having no real partners, are relegated as Is and IIs.

So, to summarise: for me, this is not a matter of context; all these relationships are valid in every context as long as the elements stay themselves (i.e. keep the general electronic cloud structure); and we can clearly distinguish primary, secondary, tertiary, and quaternary relationships in terms of how good the analogy of the electronic cloud structure is. This may be displayed either implicitly (teaching the idea "same distance from a noble gas or pseudo-noble gas" to avoid drawing); through extra parenthesised symbols as in DA's version above; or perhaps through something like the Bayley-pyramid arrangement. However, the electronic structures and hence the periods and groups come first, and those follow the primary relationships whenever they exist, and secondary relationships whenever the primaries don't exist. So I still promote the idea of exactly one true nature of the elements that is displayed by He-Be + Sc-Y-Lu and by no other rectangular grid form, and the idea that Lu (say) is intrinsically a d block element and that it is a mistake to put it down as f block, but that does not mean I have anything against using and bearing in mind things like Sc-Y-La or B-Al-Sc as secondary relationships cutting across blocks (as all secondary and tertiary relationships do). Indeed, I advocate remembering every one of those relationships, primary, secondary, tertiary, or quaternary, in every single context. Not "this is more useful in one context, that is more useful in another"; for me, they all should be kept in mind all the time, as long as we remember whether they are primary, secondary, tertiary, or quaternary.

Of course, you may have a different view about these things. ^_^ Double sharp (talk) 10:34, 4 October 2020 (UTC)[reply]

Totally agree with Double sharp. Droog Andrey (talk) 20:55, 5 October 2020 (UTC)[reply]

@Droog Andrey: Thank you!!! Double sharp (talk) 21:18, 5 October 2020 (UTC)[reply]

A thing of beauty

I think the pt above is a thing of beauty. It illustrates the secondary relationships in a much more economical and self-explanatory way than Sandbh's group resonances. It is if you will resonances of elements rather than of groups. I think what it expresses is identical or nearly so. It just requires less hand-waving to explain and less head-scratching to understand.

@Droog Andrey and Double sharp: Thank you for creating this pt and for bringing it to my attention. Though I am not yet prepared to give up our enwiki metalicity categories, this pt has knocked me off the fence, landing me solidly in the garden of Sc/Y/Lu/Lr.

--- preceding unsigned comments posted by User:YBG 04:21, 6 October 2020‎ YBG

@Sandbh: Thank you for signing for me! Much obliged! @Droog Andrey and Double sharp: I think my failure to sign may have thwarted the pings. YBG (talk) 04:35, 6 October 2020 (UTC)[reply]

@YBG: Thank you for your kind words. ^_^ Double sharp (talk) 20:26, 6 October 2020 (UTC)[reply]

Or is it?

@YBG: Droog Andrey's table does not address nor resolve the group 3 question. His (incomplete) table is more conveniently displayed in 18-column form. As far as the 32-column table is concerned, Nature does not care about human conceptions of beauty. I discuss this in my article. Sandbh (talk) 05:57, 6 October 2020 (UTC)[reply]

@YBG and Sandbh: It does fully address and resolve the group 3 question according to its bases, which you're of course free to disagree with. OK, it doesn't have the group numbers explicitly there, but I can add them:

Is	IIs	IIIf	IVf	Vf	VIf	VIIf	VIIIf	IXf	Xf	XIf	XIIf	XIIIf	XIVf	XVf	XVIf	IIId	IVd	Vd	VId	VIId	VIIId	IXd	Xd	XId	XIId	IIIp	IVp	Vp	VIp	VIIp	VIIIp
H	He																													(H)	(He)
Li	Be	(B)														(B)	(C)								(Be)	B	C	N	O	F	Ne
Na	Mg	(Al)	(Si)													(Al)	(Si)	(P)	(S)	(Cl)					(Mg)	Al	Si	P	S	Cl	Ar
K	Ca	(Sc)	(Ti)	(V)											(Ca)	Sc	Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn	Ga	Ge	As	Se	Br	Kr
Rb	Sr	(Y)	(Zr)	(Nb)	(Mo)										(Sr)	Y	Zr	Nb	Mo	Tc	Ru	Rh	Pd	Ag	Cd	In	Sn	Sb	Te	I	Xe
Cs	Ba	La	Ce	Pr	Nd	Pm	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu	Hf	Ta	W	Re	Os	Ir	Pt	Au	Hg	Tl	Pb	Bi	Po	At	Rn
Fr	Ra	Ac	Th	Pa	U	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No	Lr	Rf	Db	Sg	Bh	Hs	Mt	Ds	Rg	Cn	Nh	Fl	Mc	Lv	Ts	Og

So we can clearly see what it's saying. It says group 3 (the d block one, now called IIId) is Sc-Y-Lu-Lr, but that these elements have a secondary relationship (indicated by the parentheses) to B and Al in group 13 (IIIp), and also to La and Ac in group IIIf. That's a clear statement and resolution based on what was set out above regarding what we consider the fundamental properties of the elements. Of course, whether or not it convinces you depends on whether or not you agree with our bases, but it clearly makes a call.

I feel that this is much better shown in 32 column format. This way we can see exactly what's going on: you get a secondary relationship when two elements are the same distance away from a noble gas to the left, but not in the same group. (For a tertiary relationship, replace "left" with "right".) In other words, secondarily related elements have equal numbers of valence electrons, and tertiarily related ones – valence vacancies. So, you can naturally see it as what happens if you try to draw the elements "in the wrong places" by ignoring the gaps. This, I feel, is lost in the 18 column format. Oh, for sure you can display it in something like Bayley's pyramid arrangement too, but the point stands; cutting out the f block elements doesn't help. In fact it makes it harder to see what's going on because of the visual break IMHO.

Some of Sandbh's resonances are not shown in our table because they are neither secondary (isodonor) or tertiary (isoacceptor) relationships, but quaternary relationships. This is so of H-B, H-C, as well as Sc-Y-Gd. This is because there are really many such relationships (Al-Fe is another one, the diagonal relationships are also others), and the fact that these are rarely very strong because there usually is no matching oxidation state. In fact, I think Al-Fe (which he doesn't show) is actually stronger than H-B and H-C precisely because there is an oxidation state match: Al³⁺ and Fe³⁺. Whereas, good luck in finding any oxidation state matches for H-B and H-C.

Incidentally, I don't feel that Sc-Y-Gd is actually a very strong relationship either. Yes, it's true that the 4f electrons are somewhat sluggish and reluctant to participate in chemistry (though it is possible), but this is exactly why the Sc-Y-* table exists: every lanthanide looks fairly good under Y. No one can complain with La as a higher homologue of Y if it were the only lanthanide. No one could complain with Lu as a higher homologue of Y if it were the only lanthanide either. Or if it was Gd. Or if it was Ho. Or if it was Pm. (Exceptions being the ones with the +4 state.) So that's why La-Lu are sometimes taken in one space. Of course for Ac-Lr it becomes somewhat nonsensical, but again: a secondary relationship need not be universally strong (Mo-Nd is extremely weak, but Mo-U is strong).

It's not a matter of beauty: I didn't start with this beautiful form and seek to justify it. You may recall that my case for Sc-Y-Lu has nothing to do with symmetry but has everything to do with the presence of valence 4f involvement at La and its total absence at Lu. If hypothetically it were true that La had no significant valence 4f involvement but Lu did, I would be arguing with equal fervour for Sc-Y-La. But that's not the case, so I don't. So it's not a matter of symmetry for symmetry's sake, only symmetry because the data as I read it supports it. If I were going for a beautiful form first and foremost, I'd run to the Janet table, where every row beautifully has a partner and there are no gaps whatsoever. But I don't because it doesn't make any chemical sense: there's no mixing between (n−1)p and ns subshells (at least, not until relativity runs amok in a few bits of the seventh and eighth rows; using those as a justification is letting the tail wag the dog). As long as you accept our premises, you get our conclusion. If you don't, then of course it won't decide anything.

All this is of course my view, and you are of course free to disagree with it. Double sharp (talk) 10:35, 6 October 2020 (UTC)[reply]

@Double sharp: I don't follow how the group 3 issue is resolved according to its bases, as you wrote, presuming you're referring to DA's table alone (as I did).

I can see the secondary and tertiary relationships, and related elements having equal numbers of valence electrons, and tertiary related ones – valence vacancies, just as well on the 18-column form. And I don't need to scroll off the screen. In any event, I recall Droog Andrey(?) saying something like the relationships he showed were not the only ones.

I'd forgotten about Al and Fe. That's a good one, thank you, and I've added it. Among other reasons, H over C works due to both elements having half-filled valence sub-shells. H over B works on account of the twenty or so relationships I set out previously. Valence considerations are not the only things to be considered in resonance examples. H over B and C were both recognised by Imyanitov (2016). There is much more to resonance than oxidation states.

Gd was recognised as the central metal of the lanthanides by Laing (2009), hence the Sc-Y-Gd- relationship.

The reference to beauty was raised by YBG: "I think the pt above is a thing of beauty." I took this to have partly contributed to him falling off the fence! Sandbh (talk) 05:56, 7 October 2020 (UTC)[reply]

@Sandbh: Well, I explained it above, but sure, I can do it again. The basis of DA's table is that elements are defined by two attributes: (1) their atomic number, and (2) the structure of their electronic cloud.

We don't consider the differentiating electron for a couple of reasons. First of all, in the first place electrons are not distinguishable. It doesn't really make sense to pin down "an s electron" or "a p electron" when there is literally no way to distinguish between any two electrons. Please, see the article

Identical particles

. The electrons all have the same properties and we can't distinguish them by location, because we only have wavefunctions saying where they're likely to be, and these will overlap.

Secondly, an atom of scandium is not differentiated from an atom of calcium by its extra 21st electron alone, but also by its extra 21st proton. That's important because the increased nuclear charge of the atom has an impact on the energy of orbitals. If we look at the 20-electron isoelectronic sequence, we see Ca⁰ with configuration [Ar]4s², but Sc⁺ with configuration [Ar]3d¹4s¹, and then Ti²⁺ with configuration [Ar]3d². What is happening is that 4s and 3d are very close in energy, and minor effects can shift the balance. The "competition" between 3d and 4s states is not a matter of 3d only becoming active at scandium; they're really both active already at potassium. It is actually because there are two opposing effects: (1) the 3d orbitals have a similar radius to the 3p ones in the core, and so there is a strong interelectronic repulsion that raises their energy, but (2) the 4s orbitals have some amplitude near the nucleus and feel its attraction more. The need to balance interelectronic repulsion is, as Richard Feynman points out in his lectures, the reason why the Madelung anomalies occur. But he is also quick to point out that the precise configuration actually can be impacted by the surrounding chemical environment:

“

In copper an electron is robbed from the 4s shell, finally completing the 3d shell. The energy of the 10, 1 combination is, however, so close to the 9, 2 configuration for copper that just the presence of another atom nearby can shift the balance. For this reason the two last electrons of copper are nearly equivalent, and copper can have a valence of either 1 or 2. (It sometimes acts as though its electrons were in the 9, 2 combination.) Similar things happen at other places and account for the fact that other metals, such as iron, combine chemically with either of two valences.

”

As a minor example of this: remember when I said Ti²⁺ is [Ar]3d²? That's true when it's alone, but in TiO it's closer to [Ar]3d¹4s¹!

If we increase the charge, the nuclear attraction wins, and all the Madelung anomalies go away. Sc²⁺ to Zn²⁺ are consistently [Ar]3d^1–10. And this is more or less what happens in a chemical environment; outside strongly ionic compounds, a metallic element due to charge-transfer will not have its "theoretical" oxidation state, but some fractional charge between 1 and 2 (for example, VCl₄ has formal V(IV) but is closer to V²⁺). This sort of ligand-to-metal charge-transfer is not an unusual thing. It is absolutely common in the entire periodic table.

Further information about this, including the above example can be found in C. Jørgensen's article The Loose Connection between Electron Configuration and the Chemical Behavior of the Heavy Elements (Transuranics). Here he gives the f elements too as examples. Here, because 4f is close to the nucleus and in a region of even higher electronic density, the effect is even larger, and at low charges we cannot avoid occupancy of 5d (which is in a region of slightly less electronic density). But the effect as above still happens: La⁰ has [Xe]4f¹6s² almost 2 eV above the ground state (which is still well within reach of chemical effects), but with La²⁺, [Xe]4f¹ is only about 1 eV above. For cerium it passes zero; Ce⁰ [Xe]4f¹5d¹6s² ionises to Ce²⁺ [Xe]4f². The issue for lanthanum is not that 4f isn't participating in chemistry; it's just that, in the very special situation when a La atom is alone with nobody else around, over a xenon core, with this not-so-high nuclear charge, putting an electron in 5d rather than 4f lowers interelectronic repulsion. If other atoms are around, then 4f may very well be partially occupied, as we showed in the previous megathread with citations. It's the exact same story with Gd because of the stability of f⁷: f⁷d¹ leads to less repulsion than f⁸ (the latter completing the first spin-pair). Notably this shows that it's really Eu that is the homologue of Mn. Just like Cr as an atom attempts to mimic the half-filled d⁵ configuration to lower interelectronic repulsion, Gd is mimicking f⁷ to do the same. The 5d¹ occupancy at the beginning, like the 6d¹ and 6d² even at the beginning of the actinide series, is not a reflexion of a filling process where 5d fills and hangs up before 4f; it is rather that 4f and 5d are now both chemically active, but interelectronic repulsion results in an early filling of 5d just as it did for 6s!

As such, I consider it as clearly demonstrated that looking only at ground-state electronic configurations and differentiating electrons is not a sound basis. Reliable sources clearly understand this.

BTW, the fact that it's so well-known that ground-state electron configurations for the d and f elements are problematic is part of why I lost my cool and got frustrated with you in the previous megathread. I am sorry for it, but I still counsel: please, this information is so standard it even made the Feynman lectures on physics. Please, I counsel you, please give up on ground-state electron configurations and differentiating electrons. It will not do you any good. Please.

Well, let's go on. Despite these words against the exact ground-state electronic configurations and differentiating electrons, it remains that electronic structure is the mother of chemical properties. Some sort of understanding of electronic structure is needed to explain why the periods are the lengths they are. True, there are many effects; we can't for instance derive oxidation states from electronic configuration, especially all the more so because oxidation state stability is so strongly dependent on the ligands and charge (compare XeF₈ vs XeO₄, or TlI₃ vs TlI₄⁻). But it all comes from there because the outer electrons are participating. That's why we have been saying; let's focus on the orbitals that can be involved in chemical reactions and their occupancy.

Done like that, the group 3 situation is immediately resolved 100% in favour of Sc-Y-Lu. Because we have the following situation:

Element	Chemically active subshells	Total occupancy of chemically active subshells
B	2s, 2p	3
Al	3s, 3p	3
Sc	3d, 4s, 4p	3
Y	4d, 5s, 5p	3
La	4f, 5d, 6s, 6p	3
Lu	5d, 6s, 6p	3
Ac	5f, 6d, 6s, 7p	3
Lr	6d, 7s, 7p	3

The situation is clear. Scandium and yttrium use s, p, and d subshells for their chemistry. Lutetium and lawrencium are the same and act as true higher homologues; they match everything except for the principal quantum numbers of the subshells involved. They have a primary relationship, all four being (dsp)³, and therefore immediately go in the same group. But lanthanum and actinium are not the same; they also use their f subshells. These elements are rather (fdsp)³. True, they have a secondary relationship to Sc and Y, because they do still have three valence electrons, outside a noble gas core either. That is why trends going down Sc-Y-La, as well as Sc-Y-Lu, both look fairly convincing. And these trends are both valid, not only in their own contexts, but in any context. In all contexts, the relationship of yttrium to lutetium is important, and the relationship of yttrium to lanthanum is also important. But from the fundamental perspective of the electronic structure that is the genotype of the elements, Y-Lu must be admitted as the primary relationship.

Finally we can see the analogy. Boron and aluminium are (sp)³. Their true primary relationship is of course to gallium and its heavier congeners, which are also (sp)³. But they also have a relationship indeed to Sc and Y which are (dsp)³, and also to La and Ac which are (fdsp)³; all of B-Al-Sc-Y-La-Ac are three electrons over a noble gas, and for that reason they have some similarities. That's not a problem considering that the path from electronic structure to chemical behaviour is full of twists and turns. But we should understand that it's electronic structure that gives us our periodic table, not the matching of chemical properties, as should be clear from the placement of nitrogen and bismuth in one and the same group which are as different as chalk and cheese.

When element 121 is discovered, it will have three valence electrons with participating orbitals 5g, 6f, 7d, 8s, and 8p, and it will therefore immediately start a group IIIg. And this region of the table is the last death knell for ground-state gas-phase electron configurations: many superactinides don't even have a single such configuration, because too many configurations are too close to each other.

To summarise; under our paradigm, Sc-Y-Lu is fixed extremely simply by exactly one argument: the presence of significant 4f involvement on lanthanum, and its total absence from lutetium. Group 3 is resolved as Sc-Y-Lu. The duplication of parenthesised (Sc) and (Y) symbols over La, without any block colour, simply means that these elements have a secondary relationship to La that should not be forgotten. But it does not mean that La is a member of group 3. It still is not.

I know it's difficult to let go of Sc-Y-La; I know it's common; I know it's also difficult because you just got an article published supporting it. I really understand; remember, I worked with you on the 2017 IUPAC submission, I had a stake in the Sc-Y-La form as well. But, after some vacillation, I eventually let go of it. Sc-Y-La just doesn't reflect the fundamental properties of the elements very well and confuses the issue. The basis of the periodic table is not the final chemical properties (if not, N and Bi would never have gotten into the same group – not to mention N and Mc, since Mc shouldn't even have the +5 oxidation state), but fundamental properties that help to rationalise those things in the end. (And even if it was about the final chemical properties, there is not a difference between groups 3 and 4 that is not equally apparent between groups 13 and 14.) I discarded it quite reluctantly, but I did it in the end.

I'd like to just add that what convinced you to Sc-Y-La in the first place (previously you were favouring Sc-Y-Lu) was something I said in 2016 when I knew less on my talk page. Now I've learnt more, and I counsel; actually, I don't think it works anymore. I would be glad to explain to you again why I think it doesn't work anymore. But, please, listen to me. I do not like to see you using things that have been superseded in the literature. I know you want to know more about periodicity. Please, don't take this all as too complicated. Please understand: the point of science, as Feynman noted, is "understanding basic phenomena in terms of the smallest set of principles". It's not about how deep we're drilling down; indeed we are expected to drill down very deeply to do it. That's the basis of reductionism. It's about how much understanding we get from just a little. Sc-Y-Lu can help. I know I and Droog Andrey have been harsh, but at least for me, it's partly because I cannot bear to see you continue with misunderstandings and using simplest sufficient complexity, not in how it was intended to be used (Occam's razor), but to stay with something that has already been refuted.

I feel the 18-column form is not better, because cutting out the f block rather makes it more difficult to see the point: elements that are secondarily or tertiarily related to each other are the same distance from a noble gas, skipping the blanks. So you can find some secondary relationships by drawing the elements again in a way that ignores the gaps. This neatly rationalises the f block relationships in a way that I feel becomes significantly less obvious if we cut out the f block (so that the fifth period no longer neatly seems to go Rb-Sr-(Y)-(Zr)-(Nb)-(Mo)-... and then -(Sr)-Y-Zr-Nb-Mo-Tc again). Incidentally, it seems to me that whether or not we have to scroll off the screen is not so much a matter of Nature as it is a matter of aesthetics and technical limitations. ^_^

There is indeed more to it than oxidation states (otherwise the diagonal relationships wouldn't mean anything), but it seems to me necessary to have some sort of oxidation state match if you're going to have a relationship that's strong in any way. You may recall that I strongly criticised your approach towards H over B there as a bunch of disconnected facts. While I think my tone was a bit too harsh, I still agree with my sentiment.

“

It is, in fact, very simple to decide what observations are to be regarded as trivia. How connected are they with everything else in chemistry? And can such arguments be produced for almost any combination of elements? The latter would be a strong argument to consider an observation trivial. You "make an observation and proceed from there to see if other observations, including those made in the literature, are supportive". But do you look for the avalanche of other observations that are not supportive? I add the Wason selection task with its picture straight from its article as an illustration and a question. ... Double sharp (talk) 07:54, 14 June 2020 (UTC)

”

That's the standard I counsel that you hold yourself to. Please, don't just look for things supporting what you like. In order to truly prove something, you need to try to knock it down. By all means, formulate hypotheses to your heart's content. But then pretend you're neutral about it. And ask yourself: "OK, pretending that I don't know the answer like I didn't a few months ago, would this convince me? And what would convince me that this isn't right?"

I close with a quote from Sengcan:

“

If you want the truth to stand clear before you, never be for or against. The struggle between 'for' and 'against' is the mind's worst disease.

”

Yes, we all have our preferences. But when searching for truth, we have to try to pretend they're not there.

Maybe YBG thinks DA's form is beautiful. But he said something that in my view is more important. He said "It illustrates the secondary relationships in a much more economical and self-explanatory way than Sandbh's group resonances. It is if you will resonances of elements rather than of groups. I think what it expresses is identical or nearly so. It just requires less hand-waving to explain and less head-scratching to understand."

That's what I think science should be here for: explaining the most with the least. That's simplest sufficient complexity as it was always intended to be. Explanatory power is beauty. Double sharp (talk) 10:46, 7 October 2020 (UTC)[reply]

@Double sharp: I understand all of this. As you have explained it to me, it is not DA's periodic table per se that provides the basis for Sc-Y-Lu-Lr, it is (1) atomic number, and (2) the structure of the electronic cloud. Do I have that right? Sandbh (talk) 05:59, 8 October 2020 (UTC)[reply]

@Sandbh: Yes, that's correct. DA's periodic table is just also based on those two. Double sharp (talk) 08:22, 8 October 2020 (UTC)[reply]

Resonances not recognised

@Double sharp: I didn't recognise C-Si over Ti as a resonance. That was a judgement call. G&E mention the relationship between group 4 and group 14 very briefly. There is not much to it. Siekierski & Burgess (2002, p. 104) write, "In fact, except for the maximum oxidation state +4, the Group 4 elements have little in common with the group 14 elements, even with the three heaviest (Ge, Sn, Pb)."

I ignored DIM's 8-column table as I was concerned only with the 18-column form. I have read criticism of much of DIM's mixing of the A and B groups as being largely shallow. But that may be a Western bias. I do however recognise the n, n+10 relationships seen in the 18-column form.

It seems to me that whatever the resonance, some forms do a better job showing the periodicity of some properties than other forms. That applies regardless of the basis for choosing the form in the first place (which should always be set out up front). That was what I tried to emphasise in my article. Sandbh (talk) 00:58, 6 October 2020 (UTC)[reply]

@Sandbh: On the contrary, there is quite more than that, as expressed in Rayner-Canham's article. TiCl₄ and SnCl₄ are both tetrahedral and hydrolyse in water (that's also true of all the group 14 tetrachlorides), but more than that have very similar melting and boiling points. TiO₂ and SnO₂ are isostructural, and reversibly change colour on heating. More than that, but vanadium also shows significant similarities with phosphorus. And in fact, DIM's 8-column table with the A and B groups in the same columns works precisely because of the n, n+10 relationships. And these similarities seem to me to be way stronger than whatever similarities can be found for hydrogen to carbon; at least these actually share a common oxidation state. As we know, stoichiometry is extremely important in chemistry: that's why Mendeleev's table had the formulae for hydrides and oxides listed (R₂O, RO, R₂O₃, etc.).

All the periodicities always exist, and as shown above it seems to me perfectly possible to create a table that shows all the ones with chemical significance, while stressing exactly how they arise. (Of course something like the lack of Zn-Cd-Dy being shown doesn't bother me; yes, technically, formally it is a valid secondary, but it has zero chemical meaning.) As you know, I do not feel that there is a need to set out the bases universally because it seems to me that electronic structure, being as fundamental as it is, is a good enough basis for pretty much every normal use case. Let me repeat for clarity: I don't consider the situation to be "in some cases one resonance is more important and in other cases another is more important". I consider the situation to be "in all cases all resonances are important and should be understood". For me it's not "sometimes Sc-Y-La is better and should be shown, sometimes Sc-Y-Lu is better and should be shown"; it's "Sc-Y-La and Sc-Y-Lu are both always important and should be understood, but it should also be understood that the first is secondary and the second is primary". That's why I favour either explaining how to get secondary and tertiary relationships (count equal columns ignoring f and/or d block gaps from the edges of the table), or using parentheses to explicitly show the most important ones.

In fact, I actually think that overemphasising one resonance at the expense of others can be quite harmful. I would consider that a form with explicit Sc-Y-La actually does a worse job at showing the resonance Sc-Y-La than a strict Sc-Y-Lu or the one above, because it gives the implication that Sc-Y-La is a direct, primary relationship, that there is no significant 4f involvement in La, that there is a markedly stronger 5f involvement in Th, and that Sc-Y-La is a significantly stronger resonance than B-Al-Sc because the latter isn't shown. I think the data is against all of these statements. And I think the absence of La from at least one study of 4f involvement in the lanthanides (here it is) may be a bad consequence of the common Sc-Y-La form; because La visually appears to be before the 4f series, that may contribute to people not investigating its 4f involvement precisely because they think there's no point and that it can't have any. (Yes, the same problem would impact Lu if Sc-Y-Lu were the common one, but at least then it's actually correct that Lu doesn't have any significant 4f involvement, and we know it because it's been investigated in that paper; if even hyper-electronegative and small fluorine and oxygen cannot coax it out, like can happen for Zn 3d, then it's just not going to happen.) But you may disagree. Double sharp (talk) 10:35, 6 October 2020 (UTC)[reply]

@Double sharp: Thank you. Yes, I now recognise the C-Si over Ti relationship. H over C (or B) I've addressed above. Yes, I agree with you. Overemphasising one resonance at the expense of others is unhelpful. They all have validity within the applicable context. I said previously that electron structure is fine for its context and that, as with all attributes of interest, it shows some aspects of periodicity no better or worse than others. As noted in my article it is ironic that, akin to a game of whack-a-mole, attempts to improve regularity in the appearance of the periodic table increases the number of irregularities amongst various other properties and relationships across the table, and cognitive dissonance with respect to chemical relationships between or within groups or series of elements. Like Plato's cave, no form of PT is capable of capturing all aspects of periodicity.

@Sandbh: Please, see my response in the previous section. Double sharp (talk) 10:48, 7 October 2020 (UTC)[reply]

A "radical" eight-colour scheme

This is about the number of categories, not their associated colors

​​​​ This proposal is based on the following premises:

1. Scerri's contention that, “The periodic table has now become as much the property of physicists, geologists, astronomers and others as it is of its chemical originators.” (2020b, p. 7).
2. Our periodic table article is an article about the periodic table rather than a strictly chemistry-based periodic table.
3. In this context, the AE and AEM are not worth separate colour categories, for the literature-based reasons set out previously.
4. The Ln and An can be marked as such, rather than needing separate colours.
5. YBG's preference for fewer categories per 7±2
6. The most common names found across the literature for each category.

Premise #2 is the most important premise. Not observing it has been the cause of all our difficulties. IUPAC does not own the periodic table.

The radical proposal has four metal categories; one metalloid; and three nonmetal. Given metalloids have a predominately non-metallic chemistry, this results in four metallic and four non-metallic categories. Speaking boldly, as I see it, it appears to be the first table to solve all issues raised in past discussions. Note the treatment of Al (per Deming), Th, Lu and Lr.

Whatever you believe is missing or should be removed can be added to the categories section of our periodic table article.

It was liberating to throw off the IUPAC shackles and to apply more of a cross-disciplinary perspective rather than being unduly concerned about what a chemist would think. Chemists don't own the periodic table.

Could you please let me know how it looks. Sandbh (talk) 11:19, 6 October 2020 (UTC)[reply]

@Sandbh: In fact, I don't like it; my apologies for that. Whatever reason there may be for it, it remains that AM and AEM are way more common than "pre-transition metal". And of course, there's no way to appeal to all groups simultaneously. I suspect that astronomers are going to be much more interested in how the elements were made (BBN, stellar nucleosynthesis, s process, r process, p process, decay chains, synthetic) than their actual properties. And as I said above, although one may argue about how chemists shouldn't own the periodic table, the fact of the matter is that they are de facto its custodians, with some joint ownership from physicists. Which organisation makes statements about categories? IUPAC. Which organisation is deliberating the group 3 issue? IUPAC. Which organisations evaluate discovery claims for new elements? IUPAC and IUPAP – and there are complaints that IUPAC dominates the process too much, because this is more physics than chemistry and has been ever since nobelium and lawrencium were discovered, but chemists cling to the process! So we should, IMHO, continue to be concerned about what chemists would think.

I continue to prefer either V5a with "other nonmetals" instead of "light nonmetals", or no change from status quo. That's also a compromise on my part: my secret inner preference is what I show at User:Double sharp/Periodic Table (only blocks + metal/nonmetal; of course, those group numbers need some outside appearance first). It seems to me that V5a with "other nonmetals" has a chance of getting a consensus: things near the edges (throwing out categories or throwing out IUPAC) seem unlikely to get a following, but something near the middle probably has more of a fighting chance. So, whatever we really want deep down, I suggest we stick to a compromise that everyone at least can agree is an improvement over the status quo, rather than try to change a lot at once and end up in a situation where everyone wants a change, but no one can agree on what the change should be to, and so nothing happens. Double sharp (talk) 11:27, 6 October 2020 (UTC)[reply]

@Double sharp: Thank you; no need for apologies ^_^ All part of the discussion process.

Please correct me if I am misguided: our periodic table article is about the periodic table in general, across all disciplines. It is not the periodic table (chemistry). If the latter was the case, then sure, AM and AEM stay. Even then, the chemistry literature recognises the difference between the two categories is more of degree than kind; and that the chemistries of the two categories resemble one another to a large degree!

Appealing to all groups simultaneously is not required. I suggest we are obliged to, in the best encyclopedic tradition, give due consideration across disciplines, rather than paying undue heed to chemistry, chemists, and IUPAC.

IUPAC relevance is limited and mixed. Yes, with IUPAP, they recognise and approve names for new elements.

While IUPAC also approve names of sets including (a) AE: (b) AEM; (c) lanthanoids; (d) actinoids; and (e) rare earth metals, items (c) and (d) are widely ignored in favour of lanthanides/actinides; and "REE" is more common than REM. IUPAC further incorrectly note groups 3−11(12) are commonly referred to as "transition elements" whereas the elements involved are actually way more commonly referred to as transition metals. Even Jensen, a chemist, off-handedly disparaged IUPAC:

"As scientists we should base our conclusions on a critical examination of the chemical and physical evidence and not on an appeal to authority or the arbitrary whims of committees and popularity polls. Above all, such demands should be tempered by the sobering recollection that IUPAC is the organization that brought us density in units of kg/m3, 4πε₀ in the denominator of Coulomb’s law, and the finger-count labels 1–18 in the periodic table."

Not forgetting IUPAC are of no help with regard to nomenclature for the so-called post-transition metals; metalloids (repeatedly criticised by them, with their confusing suggestion to use "semimetals" instead never mind the mix-up with the physics-based sense) and the orphan nonmetals.

I contend the views of the metallurgists and representatives of the 19 other fields of study I mentioned in "notes on the other nonmetals", here, are as important as those of chemists.

I like V5a too. Houston, we have agreement. Yahoo!

I wouldn't've posted this radical proposal but for Scerri (chair of the IUPAC group 3 project, no less) writing that the PT has now become as much the property of physicists, geologists, astronomers and others as it is of its chemical originators.

I agree the way ahead in terms of introducing possible change requires careful consideration. I'm not there yet; I'm still in the background-information-gathering, discussion, and sounding-out stage. Sandbh (talk) 03:08, 7 October 2020 (UTC)[reply]

@Sandbh: Except I am not convinced at all about how you interpret what Scerri says. As a statement that the PT is used also significantly by those other fields, surely I agree. But I don't agree that they have equal relevance when it comes to the categories used on the PT, and I don't see that in what he says. Exactly what are those other disciplines using the table for, if not to rationalise the chemical properties of the elements that are of interest to them? That's not so much another claim to the table, in my opinion, as it is. The fact of the matter is that IUPAC is the organisation making statements about the periodic table. Sure, they're not always listened to, but apart from a few things from IUPAP no one else is doing it. Is there something similar coming from geologists or astronomers? I rather doubt it but I'm ready to be convinced if you can show me such.

What Jensen says is completely, 100%, correct when it comes to the situation he's writing. It is, however, not correct for Wikipedia. The whole thing about

WP:NOR

is precisely about appealing to authority and popularity polls; you need to reflect the situation in the literature and not add something to it even if you feel the situation is completely inadequate. And that's exactly why, even though I agree with you that the difference between AM and AEM is not that significant (it's really just valence), I still oppose getting rid of them as categories. On WP, we're supposed to reflect the literature and not try to change it. That literature, as I see it, seems to be that chemists are de facto first among equals when it comes to deciding what the PT looks like, with physicists as a close second and everyone else far behind. Whatever you think about IUPAC (and I admit I'm not that impressed by them all the time either), it remains that we don't have much else that's better.

Anyway: I think V5a is good, except that I would prefer "other nonmetals" still for the above reasons. In fact, I would even prefer "other metals" because Post-transition metal#Related groupings shows that there's lots of names for this or a similar set of elements, none of which have any sort of official stamp, and none of them are really dominating in the literature. I think an "other" category better reflects that. And besides, I think having "other" categories is more or less forced on us by the simple fact that these categories were never really intended to become exhaustive and mutually exclusive in the first place; they were just invented to group similar elements together. It's not particularly surprising to me anymore that an element like hydrogen with such unique chemistry is very difficult to put in anything other than an "other" non-category. But to me, that's not like throwing it into a dustbin, but an acknowledgement that these elements are really special and don't fit well into categories grouping together similar things. But, since "post-transition metal" at least seems to have more currency in the chemistry-based literature than "light nonmetal", I won't insist on changing to "other metal" as well. Double sharp (talk) 11:24, 7 October 2020 (UTC)[reply]

@Double sharp and YBG: I note:

• IUPAC only "approves" collective names for like elements.
• The use of these names is not mandated.
• IUPAC has not approved a collective name for group 3 to 12!
• As you note, and I suspect R8R might agree, the divide between the AM and AEM is more a divide for the convenience of having a divide, rather than a divide of major significance e.g. between blocks, or within the p-block, where all kinds of hell break out.
• From the COPTIC database of 62 more recent chemistry textbooks, AM and AEM have only a 10% appearance frequency!
• The higher level PT graphic is not the same as the detailed contents found in an actual chemistry textbook that would mostly include e.g. a group-by-group discussion of the TM or the light TM in period 4 and the heavy TMs in periods 5-6. Thus, why do we not separately colour-code each individual TM group or p-block group on our graphic? Because the great majority of chemistry text-book authors recognise the distinction between a higher-level graphic, and the main corpus of the book.
• Deming, a chemist, and the guy who popularised the 18-column table, sensibly wrote that the AM, AEM, and Al were light metals. He retained the AM and AEM nomenclature, but gripped up the two sub-categories into the LM category. And in his chapter on the LM, after discussing their shared properties, he still allocated separate sections to the AM and AEM, and Al, since that is what a text book is for.
• D thereafter distinguished between the transition heavy metals (groups 3-10); rare earth metals; and the heavy or post-transition metals (groups 11-16). In the rest of his book he had chapters on hydrogen; the halogens; the sulfur family (group 16; why the "sulfur" family?); nitrogen; carbon; and silicon and boron.
• There is no basis in the literature, per the COPTIC database, to insist on the inclusion of the AM and AEM on our PT graphic (as opposed to any footnotes).

Per YBG, 4+4 is all we need in our graphic. Sandbh (talk) 07:30, 8 October 2020 (UTC)[reply]

---

• Please please keep distincting "colours" and "categories". We can have 'category' talks, and 'color' talks separately. -DePiep (talk) 21:21, 7 October 2020 (UTC)[reply]

ACS Division of Inorganic Chemistry 32-column PT Logo

It seems they have revered to the La form, judging by recent e-mails I have received from them.

That is odd, since Eric had reported the logo was withdrawn due to the controversy associated with the Group 3 question. See note 15, here. Indeed I remember getting e-mails from the ACSDIC with a 32-column Lu logo. I remember thinking at the time that was an odd choice since it replaced one controversy with another.

I have no idea what's going on. Sandbh (talk) 03:23, 7 October 2020 (UTC)[reply]

If we really want the "Other" categories

It might be acceptable if the legend were presented like this:

Active metals   Inner transition metals   Transition metals   Other metals

Noble gas nonmetals   Halogen nonmetals   Other nonmetals   Metalloids

My point here is that if we have "other" categories, those categories must come at the end of the list ... other metals at the end of the metals, and other nonmetals at the end of the nonmetals. Note that by this graphic I am not endorsing a particular scheme. my main point is simply that the "other" must clearly be at the end of the list.

This legend includes some things that I like and some that I abhor.

1. I prefer "Active metals" to "Light metals" for a number of reasons, but primarily because it makes more sense to me and because I'd prefer to exclude Aluminum..
2. I prefer "Inner transition" because I think it is a well-known term and because by combining the Ln and Ac we reduce the number of categories. My only hesitation is that I don't know if the two series are chemically similar.
3. I rather like PTM, but the point here is to illustrate how to incorporate "Other-X" category names. But it is nice to have two parallel "Other" categories, M and NM.
4. I use "noble gas nonmetals" intentionally, so that it it is clear which categories are nonmetals and that metalloids are not nonmetals.
5. I still dislike separating the reactive nonmetals, but it is nice to have four categories on each side.
6. I dislike the term "halogen nonmetals" and I dislike subdividing the reactive nonmetals, but if you must have the split ...
7. I dislike the "Other nonmetals" name, but I find it significantly better than "light nonmetals", which unfortunately excludes the 2nd lightest nonmetals (He) making the name seem misleading, and of course, there is the unfortunate issue of including Se which is sometimes called a heavy metal. Very puzzling for something to be categorized both as a heavy metal and as a light nonmetal.
8. I am making no statement about color choice; I merely tried to stay as close to what we have as I could.

A few additional notes

• I find it a but disingenuous that I use terms like "prefer", "like" and "dislike" as it makes everything seem to be a matter of personal esthetic preference. Well, in many ways, that is what it is. And frankly, I prefer (!) prefer/dislike over other ways of expressing things given recent difficulties which have made the past few months sadly the most un-collaborative I have experienced in my years at
  WP:ELEM
  .
• The main point of this post is simply that if we wish to restore "Other-X" categories, a legend scheme like this just might avoid the horrid sound of the "other-X" category names.
• If we end up with more than eight categories, I have no idea how the legend could even approach being aesthetically pleasing.
• I am fully aware that using a legend like this would wreak havoc with the legend options in our PT templates. Resolving that issue is by no means trivial, and I will say this: if we cannot figure out a way to present "Other-X" as last in the list of X's, then I would oppose the resurrection of those category names. For me, this is a non-negotiable, trumped only by my respect for consensus.

--- YBG (talk) 07:37, 7 October 2020 (UTC)[reply]

@YBG: Let me answer briefly:

1. I still don't like "active metals". These are not the only active metals around; the early lanthanides are pretty reactive too. I'm against getting rid of AM and AEM here just because these names are way more common in the literature than any name for a combination of the two. And they are distinguished in one particular way; the valence (almost always +1 for AM and +2 for AEM).
2. The Ln and An are not that chemically similar (which is mostly the fault of the first half of the actinide series). On the other hand, the actinides are not even that chemically similar to each other in the first place (which is again the fault of the first half of the actinide series). Such a unified category would probably be OK because it would have about the same amount of internal diversity as the transition metals. The only problem is that "inner transition element" is defined by IUPAC as the f block and therefore I am hesitant to suggest it because it depends on the group 3 issue. Now, I know you,
   WP:CHEM
   should probably also be considered. I have posted something about the group 3 issue above, so we can discuss it there. But because this is somewhat fraught, I would probably avoid suggesting Ln and An unification until a real consensus rather than an agreement to disagree arises here on group 3 (assuming it ever does).
3. I do like "other metals" for WP. I think, we have to admit from the list at Post-transition metal#Related groupings that there isn't really a single name for the elements in this category, so in my view we shouldn't create one. "Other" may be wringing our hands in despair, but at least it's justified despair. Same goes for "other nonmetals".
4. I like putting the "other" categories at the end of our list. It makes it very clear that they're the leftovers.

In fact, I think it's good to have "other" categories because it makes one thing pretty clear: these categories were never supposed to be exhaustive in the first place. They were not invented to fulfil your rules, but rather to lump together some sets of elements that are pretty similar to each other, with no worries about whether an element ends up in more than one category, or if some elements end up outside categories. (Hydrogen, having a very unique chemistry compared to everyone else, seems almost guaranteed to end up as a leftover, for example.) So to some extent, I think the fact that avoiding "other" keeps giving us awkward names that are not quite standard in the literature suggests that we have the wrong goal here. Double sharp (talk) 11:14, 7 October 2020 (UTC)[reply]

+1 for 4+4. @Double sharp: Could we not "flag" the AM and AEM per the radical proposal? Sandbh (talk) 06:31, 8 October 2020 (UTC)[reply]

Some passing comments, which will be buffeted by the outcome of other discussions:

• “Pre-transition metals” is a crisp term for groups 1–2 and Al (noting the Be-Al diagonal relationship) and is found in the chemistry literature; see e.g. Inorganic chemistry by Cox (2004, p. 185).
• “Poor metals” is ×12 times more common than post-transition metals.
• ”Light metals” is ×14 times more common than poor metals.
• There is no puzzle about Se. It’s sometimes classified as a heavy metal since its waterborne chemistry is similar in some respects to that of As and Sb. By its density it’s a light metalloid even though it’s more generally recognised as a nonmetal proper. It’s the usual fuzziness at the boundaries
• Inner transition metals is fine; IUPAC only comments that the f-block elements are sometimes referred to as inner transition elements, that is all. Even then inner transition metals is more common.
• Other categories are preferably avoided, IMO, as they result in a lack of considered study of the attributes shared by the elements in question, not to mention a multiplicity of category names. Sandbh (talk)

Regarding the latest additions to Periodic table

I have to admit that I am not too happy with User:Sandbh's additions on categories to the Periodic table article. I have not reverted anything, it is all still up there, but I would like to discuss it here.

(Forgot to link to what I was talking about: it's the section Periodic_table#Categories. Double sharp (talk) 20:53, 8 October 2020 (UTC))[reply]

The first complaint I have is that there is a great paucity of citations. That does not seem proper for an

WP:FA

.

The second one I have is that the text does not appear to be NPOV, but rather skews towards overemphasising things Sandbh seems to be personally in favour of, and underemphasising things he seems to be personally not in favour of.

• The viewpoint Sandbh favours that the alkali and alkaline earth metals are not really that different from each other in kind, just in degree, is given prominence by collecting them as one section and explicitly saying it. Certainly, there is a citation – but is this really a representative one? Most books seem to treat the two categories rather separately. Pretty much every chemistry text that's organised by group like Greenwood & Earnshaw or Holleman & Wiberg would do so. There are many opinions in the literature, but is this one that is common enough to put into an introductory-level article like periodic table?
• Sandbh calls out the noble metals as a separate category in themselves. Again, that's something he's proposed before. But that category has a fuzzy border and is not often used to explicitly divide the table up this way. Worse, he excludes Ag from the list of the metals that are generally included as noble metals, and writes a note saying "Silver is too reactive to be considered as a noble metal". Why? On the basis of one source (Rayner-Canham) that does so. The source says "This author would contend silver is so much more chemically reactive…that it should not be considered as a 'noble metal.'" So that's what one author thinks. Does that justify a bald statement "silver is too reactive to be considered as a noble metal" without any attribution, as if this was something generally agreed like "silver has atomic number 47"? Moreover, that says nothing about whether or not Ag is generally included. On the contrary, if you go to noble metal, you will see a cited statement (to Holleman & Wiberg, a standard German inorganic chemistry textbook) that Ag is among the metals generally included as noble. It would be a reasonable reflexion of the sources, IMHO, to say "Ru, Rh, Pd, Ag, Os, Ir, Pt, Au are generally considered noble metals, although concerns have been raised about Ag due to its greater chemical reactivity compared to the other seven". But to leap to the idea from one voice of dissent that Ag suddenly isn't generally included as a noble metal seems to not follow what the sources actually say.

Every one of these viewpoints given prominence, that I mention above, is one that Sandbh has made statements favouring. Other viewpoints are not listed. And to make things clear: I do not have a general automatic feud against whatever Sandbh says, and I even agree with the viewpoint he favours about the alkali metals and alkaline earth metals. This is about

WP:UNDUE

in my opinion.

• The pnictogens and chalcogens are
  IUPAC-approved category names (names for sets of like elements); surely, as IUPAC is the International Union of Pure and Applied Chemistry, their statements are worth considering. See p. 51
  of the 2005 Red Book. In fact, it seems to me that their statements are more worth considering than those of non-IUPAC-approved categories like "noble metals". Yet if you read the section on categories you would get no indication that "pnictogen" is a category name. You would only get, in a later section, the indication that it is a group name – which IUPAC does not say. So we currently have IUPAC-approved categories getting less weight than non-IUPAC-approved categories. Is this a fair reflexion of the status of IUPAC?
• Sandbh writes "Lanthanum and actinium in group 3 are shown as a lanthanide and actinide respectively yet both are also transition metals", presupposing that La and Ac are in group 3 without any mention of the controversy. It is, as clearly stated in Periodic_table#Group_3_and_its_elements_in_periods_6_and_7, not agreed in the literature whether La and Ac are in group 3, or Lu and Lr are. I think my work-in-progress list of sources speaks for itself. This could so easily be written around just by saying "The heavier members of group 3 are shown as a lanthanide and an actinide, yet both are also transition metals". But he doesn't do that. And, of course, Sandbh has been a strong advocate of the -La-Ac form here for months, and has recently published an article presenting arguments in support of it. Even if it's not his intention to be biased towards -La-Ac here (and I don't think it is), this sort of thing, combined with earlier not giving a note about group 3 on his preferred PT images until I stepped in and suggested it (while other notes about things he was interested in were present), makes me concerned.

(Added later: I understand that this is likely to be unintentional; we all have our own preferences, and no doubt they bleed out when we write when we don't think about it. But, still; I think we should do some more to curb them. Double sharp (talk) 23:11, 7 October 2020 (UTC))[reply]

But the one I have most of a complaint with is the line just before the sections for the categories:

“

Scientists need not, "lose sleep over the hard cases as long as a classification system is beneficial to economy of description, to structuring knowledge and to our understanding, and hard cases constitute a small minority."

”

This is a quote he has often referred to in our discussions here. In that context it's perfectly fine. But exactly what is it doing in this article on the periodic table? It's cited, so let's look at the citation. It's not from a book about the categories of the periodic table. It's not even a book about the periodic table. It's not even a book about chemistry. It's a book about the dwarf planet Pluto! And here are the names of its chapters:

1. The Solar System
2. The discovery of Uranus, Neptune and Pluto
3. Pluto: a diminishing world
4. Pluto's family
5. Surfaces, atmospheres and interiors of Pluto and Charon
6. The Edgeworth-Kuiper belt
7. Is Pluto a planet?
8. The New Horizons mission to Pluto [and beyond]
9. Pluto: gateway to beyond?

I admit, I haven't had time to read the whole book. I have things to do in RL and it's over two hundred pages. But these chapter titles don't give me any confidence that the book is generally relevant to chemistry at all, let alone the periodic table!

Exactly where does this quote come from? From p. 171, at the chapter "Is Pluto a planet", where classification in science in general is briefly discussed for a total of two pages (bottom of 169, 170, and most of 171). That's it. And in these two pages, the chemical elements as something to classify are not even mentioned once. The example given for the general discussion is crystals, which is at least semi-related to chemistry, but the relationship to categorising the elements into various categories is extremely strained if it's present at all. The rest of this chapter is about the classification of Pluto.

I don't see how this is relevant. How is the opinion of an astronomy professor on classification, expressed in a context that does not even mention the chemical elements, not

WP:BRD cycle: we go back to something we agree on, and discuss how to improve the version that has been boldly put up. (Added later: I'm willing to forgo the R part of the cycle in good faith, and go straight to discussion. Double sharp (talk) 23:11, 7 October 2020 (UTC))[reply

]

I have not edited anything in this section, and I'm reluctant to say this in the first place, but to me this in particular seems to be getting uncomfortably close to

WP:FA

.

So, in the spirit of

WP:BRD, could we perhaps have this addition discussed, hopefully without drama, as it is not uncontroversial? Double sharp (talk) 19:18, 7 October 2020 (UTC)[reply

]

@YBG, R8R, DePiep, and ComplexRational: I would appreciate your views on this matter as well to facilitate building a consensus. Double sharp (talk) 22:39, 7 October 2020 (UTC)[reply]

1st: Great reading, thanks for spending time on this to get it clear. 2nd: later ;-) -DePiep (talk) 22:54, 7 October 2020 (UTC)[reply]

@DePiep: Thank you, and looking forward to your view of the matter. I added a few afterthoughts above in parentheses, incidentally. ^_^ Double sharp (talk) 23:12, 7 October 2020 (UTC)[reply]

@Double sharp: Thanks for raising your concerns here rather than reverting. I like your style. I see you also gave me permission to revert one of your own edits at PT (which I haven't looked closely at yet). Nice! Sandbh (talk) 23:58, 7 October 2020 (UTC)[reply]

Sandbh comments

Preface

@Double sharp: Speaking personally, I was taken aback by how I interpreted the tenor of this post, and the words "complaint"; NPOV; WP:UNDUE (×2); WP:SYNTH; and WP:BRD. I feel there are better, more collegial ways of saying these things within a project. I feel particularly slighted by the need to invoke so many WP policies.

That said, I intend to presume

WP:GF

and respond in a civil and collegiate fashion per the sentiment of your request rather than (as I personally saw it) the superficial and hopefully unintended connotations of the words involved.

Items of concern

As I see it, all of these are easily dealt with. All the following is IMO, and shared within our project as colleagues.

1. A "great" paucity of citations. The content referred to is general knowledge. Citations are only required for "any material challenged or likely to be challenged", per

WP:FACR

In an event, anybody is welcome to add citations should they feel so inclined. When I posted the context in question it included ~10 citations. Wither great paucity?

2. Lack of NPOV?

a. AM/AEM. Consistent with most books, we continue to show AM and AEM as separate categories, with their own colour categories. Contradict me if I am wrong but the similarities between the AE and AEM are plainly evident; ask any chemist. I included two non-controversial citations. I gave another eight citations related to the similarities of the AM and AEM, here. Regarding, "…is this one that is common enough to put into an introductory-level article like periodic table?" Since our article on the periodic table is not an "introductory-level" article, I don't understand what concern is being raised here. In any event, I don't know how much more introductory it could be to note the similarity between AM and AEM. Even their names are similar.

b. Noble metals No, I did not call "out the noble metals as a separate category in themselves." What did I write? Here it is:

"Among the transition metals, the noble metals (generally Ru, Rh, Pd, Os, Ir, Pt, and Au)^{[n 3]} correspond to the noble gases.^[37]"

Note that:

• I didn't refer to the NG as a "separate category";
• I used the qualifier "generally", cognisant of what we spoke about before;
• I didn't "highlight" silver within what I said; rather, for interest, I added a footnote^[n3] (our PT article has 21 such footnotes);
• I provided an explicit supporting citation, Wiberg no less, regarding the equivalence of the noble metal and noble gas categories. Ask any chemist about this. I wiki-linked the reference to the noble metals, in the best WP tradition, so that anybody whose interest was piqued could follow up on that.

You rightly wrote, "But that [noble metal] category has a fuzzy border…". This fact has no relevance. Fuzzy borders are a general feature of classification science. At least the following of our categories have fuzzy borders: AEM (Be and Mg are not AE metals); TM; PTM; metalloids; and "other" nonmetals. I'll pick up this theme again when we get to the quote by Jones.

I do like your suggestion i.e: "Ru, Rh, Pd, Ag, Os, Ir, Pt, Au are generally considered noble metals, although concerns have been raised about Ag due to its greater chemical reactivity compared to the other seven". Perhaps we can regard Ag as the Rn of the noble metals.

Suggestion DONE. Sandbh (talk) 00:05, 9 October 2020 (UTC)[reply]

3. Other viewpoints not listed

You wrote:

"Every one of these viewpoints given prominence, that I mention above, is one that Sandbh has made statements favouring. Other viewpoints are not listed."

That's because: 1. I read, I write (here or in the article space or for the literature), I cite; I refine; and 2. I seem to be the only one with a 10,000 hour interest in

classification science matters as it relates to the periodic table. You've seen the work I did on tidying up the metalloid article, and related work on heavy metals; metal; nonmetal; post-transition metal; and my publications, submission, and articles

in the literature. And to think all that started when I saw the edit war as to which elements were metalloids, nearly ten years ago.

4.

WP:UNDUE

a. Pnictogens. Double sharp is concerned that I mention noble metals in the categories section, but not e.g. chalcogens. The latter term is recognised by IUPAC; the former is not. My understanding is that our PT categories are based on metallicity, as YBG noted recently. In that context, I mentioned the noble metals noting they correspond to the noble gases, per Wiberg. Double sharp, you mention that there is no mention of chalcogen in the categories section? Why would we do so when the categories section is about WP categories, not IUPAC-approved collective names for like elements? For that matter why do we not mention the pnictogens and the rare-earth elements (even though REM is more popular in the literature)? Why do we refer to transition metals when the IUPAC-approved name is transition elements?

b. La-Ac in group 3. That is a good suggestion. Regarding, "This could so easily be written around just by saying 'The heavier members of group 3 are shown as a lanthanide and an actinide, yet both are also transition metals.' But he doesn't do that." I didn't do that because I'm not a mind reader nor did it occur to me at the time. That's all.

Suggestion DONE. Sandbh (talk) 00:05, 9 October 2020 (UTC)[reply]

5. Most of a complaint re the quote by Jones/

WP:SYNTH

The quote, which is from a reliable source (Cambridge University Press), deals with classification science. The context for the quote is the previous paragraph in the periodic table article…

"An individual category is not necessarily exclusive according to its name, boundary, or shared properties."

…followed by three examples.

Thus, while there might appear to be some flaws in the category names (themselves derived from IUPAC-approved collective names) such as AEM, there is no real drama in classification science terms.

Similar themes, re atypical properties at the boundaries and boundary overlaps are explored in the

WP:COI

declaration: I've edited all these articles.) We have discussed blurry boundaries within our project for many years wrt to e.g. the other metals, metalloids, and other nonmetals. Similar discussions can be found in the literature concerning e.g. whether or not groups 3 and 12 are TM groups; and the location of the metal-nonmetal dividing line.

Here's a related quote concerning the importance of classification in science generally noting that, from the last I heard, chemistry is regarded as the central science:

“At any given time, during the historical development of a scientific discipline, classification of available evidence offers itself as the explanandum that asks for a theory (or alternative theories) able to explain it. But this is just one segment in a potentially unending chain of recursive relationships between classification and theory. Theory and classification indeed change over time. As a consequence, the theory that provides explanation for the data organized in a classification at a given time can influence subsequent classificatory effort, and so on. “By means of this a discipline advances: each new pattern raises questions that call for explanations, and each verified phenomenon or fact gives a new pattern” (p. 163). What counts as a fact or a theory is a matter of temporal relativity. The authors’ “concern is that we do not replace observation with theory and think that we have made some progress. Science is founded upon empirical observations, no matter how these are tied up with local and cross-disciplinary theoretical commitments or stances. Once we abandon this aspect of science…science becomes little more than a matter of worldviews and epistemic statements of faith” (p. 163).”

-- Minelli, A.: The nature of classification: Relationships and kinds in the natural sciences—By John S. Wilkins and Malte C. Ebach. Systematic Biology. 63 (5), pp. 844–846

The general discussion of classification science occurred in a science-based book, written by an Emeritus Professor, with a PhD in experimental solid-state physics, in a Department of Physics and Astronomy. While he was addressing the controversy surrounding the classification of Pluto, the principles of classification science involved are universal.

I remain genuinely puzzled as to the nature of your

WP:SYNTH

concern. Since when did we seek to quarantine and hide knowledge? A great encyclopedia illuminates the cross-disciplinary nature of scientific knowledge (as well as other kinds of knowledge).

Subject to your interest, and as warranted, I'm keen to continue the discussion in WP:CIVIL manner. I hope I've kept the SQ (snarky quotient) to a minimum. Sandbh (talk) 04:02, 8 October 2020 (UTC)[reply]

Suggestions DS1: blocks alone

Since @YBG: has previously talked about some possible category mergers, and has so far said "Though I am not yet prepared to give up our enwiki metalicity categories", here is an explanation of why I like blocks alone as categories.

Firstly, if we look only at the categories of metals, the blocks actually stand out as particularly natural mergers of similar categories.

• s-block: We are, I think, in agreement that there is not a significant difference between these (excepting Be and to some extent Mg) other than the valence. Where we disagree is whether there is a good name in the literature that has equal recognisability to the "alkali" and "alkaline earth metals" categories, that could be a replacement for a merger of the two. As expressed above, I don't think either "active metals" or "light metals" really cut it for our purposes. But it seems to me that there is a fair replacement: s-block metals. The term
  s-block
  is obviously common in the literature (IUPAC in the Red Book refers to blocks too, albeit not defining them), and it contains exactly the elements we want.

If we use an "s-block metals" category, then consistency of theme suggests that we carry on with the block theme for the rest of the categories as well. Luckily, this is almost exactly what we already have.

• f-block: YBG has previously suggested a merger of the lanthanides and actinides. I tend to agree that this would be a good idea; the differences between them are about the same order as the category-internal ones within the transition metals. It so happens that IUPAC in its Red Book already gives the name "inner transition element" for the f-block elements, so "inner transition metal" could be fine. "Inner transition element" seems to be equally official to "lanthanoid" and "actinoid". However, for consistency of theme, I think "f-block metals" would be preferred. An advantage of this is that, going one step closer to fulfilling YBG's rule #6, we lose the overlap that occurs between the Ln/An and the TM at the edges of the categories.

• d-block: The current "transition metal" category can be extended to the other IUPAC-allowed sense of groups 3–12 rather than 3–11 to match the d block. While it is true that the group 12 elements do display a significant reduction of metallic character, and a loss of the typical transition metal property of easily variable oxidation state, to my mind this is not a deal-breaker. Firstly: we used to have it this way. Secondly: it's very common to have it this way especially at the introductory level. Thirdly: in terms of coordination chemistry, the Zn group is actually not so far removed from the Cu group. Fourthly: this reduction of metallic character is more or less what you'd expect just because the block has ended – you start to get a similar reluctance to oxidise beyond +2 at nobelium as well. Fifthly: groups 3 and 4 also have weak expression of anything but the group oxidation state (even for Ti, +3 is readily oxidised to +4), as do Nb, Ta, and Db in group 5, but no one tries to remove them from the transition metals. Sixthly: the elements Zn, Cd, and Hg do show usage of their d orbitals for chemistry, which is like the metals of groups 3 through 11 but unlike the ones in groups 13 onwards. Therefore, I submit that the old group 3–12 definition, approved by IUPAC as it is, is more internally consistent with regard to how group 3 and group 12 are treated. Since the literature is somewhat evenly split, this should be no problem.

An advantage of using "d-block metals" instead of "transition metals" is that we no longer need a footnote about group 12 to be spread everywhere, incidentally.

Regarding the exact composition of group 3: I still think I am going to propose Sc-Y-Lu as the first-placed one, with Sc-Y-La as the footnote, as Polish Wikipedia does. There are a few reasons for this. It goes without saying that this is how I see the issue, and there is no obligation on anyone else to accept it.

1. This is what the majority of participants in this project's discussion have supported. I support it;
   User:Dreigorich supported it when he was here; so did User:Officer781. In opposition we have User:R8R (who seems to personally support it but have qualms regarding whether or not it's the best reflexion of the literature), and User:Sandbh
   (who, of course, recently published an article supporting Sc-Y-La). In the following points I hope to address your opposes.
2. IUPAC isn't of very much help here, because they are in the middle of deciding the issue. The 2005 Red Book shows a Sc-Y-* table, but the task force that is deciding on group 3 is explicitly not considering that as an option. The 1990 Red Book, which besides the 18 column form also shows an 8 and a 32 column form, however does show Sc-Y-Lu in the 32 column form (whereas Sc-Y-* is shown in the 8 and 18 column forms). Moreover, the context behind the compromise on Sc-Y-* seems to be between a majority showing Sc-Y-La and a minority pointing out with arguments (that convinced Fluck, who prepared this report for IUPAC) that Sc-Y-Lu was better. Therefore, as far as IUPAC recognition goes, it seems to me that Sc-Y-Lu is not out of the question.
3. If we consider the sources that consider the issue of periodic table placement, a majority tends to support Sc-Y-Lu: see
   hypervalence
   , where most textbooks will tell you d orbitals are involved for main group elements, but journal articles focusing on the matter will insist that they aren't. Here we follow the journal articles. Admittedly, the number of Lu articles is inflated by the fact that most of these authors seem to think that one argument is enough to resolve the whole issue, whereas the most prominent La article (Sandbh's) collects many arguments. While I am in agreement that really only one argument is necessary, this is a point that can be discussed. But I believe points 4 and 5, not to mention 6, partly address this.
4. Sc-Y-Lu is not confined to journal articles. It also appears both in popular science books about the elements (e.g. John Emsley, Nature's Building Blocks) and standard textbooks about chemistry: Clayden et al.'s Organic Chemistry, Jerry et al.'s Techniques in Organic Chemistry, Oxtoby et al.'s Principles of Modern Chemistry, Jones and Atkins' Chemistry: Molecules, Matter, and Charge. And, of course, it appears on the common resource WebElements. It seems unlikely to me that new readers will be unfamiliar with this form.
5. The most prominent La source, which is currently User:Sandbh himself, magnanimously notes that "different approaches to the Group 3 question...will continue to have their uses", and stresses the need to explain the relevant context. The context of this is an introductory-level article on the periodic table. The Madelung rule is surely going to be listed, but we don't really have the time to go into the individual chemistry of the group 3 elements and their neighbours as Sandbh's article does in order to support Sc-Y-La. Leaving aside the question of whether I agree or not with his analyses (I don't, and I think chemistry, while not so relevant for the question, supports Sc-Y-Lu as well), it seems to me that if the context is just an introduction with the Madelung rule given as a match for the periodic table's structure, a Sc-Y-Lu table is more appropriate for this context because it better matches the Madelung rule's statement: 4f before 5d, not one 5d hanging up before 4f starts.
6. If we are going to do a block-based scheme, then it seems to me that the argument we have stated above becomes quite important. La and Ac have low-lying f orbitals that are implicated for their chemistry, whereas Lu and Lr have no such thing. In fact, the 4f and 5f orbitals of La and Ac are available for hybridisation and are occupied in excited-state configurations that are low-lying enough to have a significant impact on chemistry, but this is not true of Lu and Lr. Importantly, this also treats Ac and Th analogously: both don't have 5f occupied in the ground state, but may use it anyway. That isn't just our original research, but is also pretty much the argument used by Jensen in this paper. It seems to me that this becomes especially important if we outright call the blocks out: it's very odd to call Lu an f block element, when it doesn't have f valence involvement. You can either take this as I do as a statement of general importance, or following Sandbh's approach as looking at the context: if the context is a block-based scheme, then Sc-Y-Lu seems more relevant.
7. The secondary relationship that even Jensen grants from La and Ac to Sc and Y seems to be slightly more graphically obvious (yes, I know, weak argument) in the Sc-Y-Lu form, than the relationship from Lu and Lr to Sc and Y is in the Sc-Y-La form. In this form, we have Sc-Y-Lu-Lr vertically aligned in group 3, but La-Ac can also be vertically aligned under group 3 and preserve the next relationships Rayner-Canham (among others) has noted of Th to group 4, Pa to group 5, and U to group 6. In the form Sc-Y-La, it isn't possible to preserve the relationship to Lu and Lr, which end up falling under group 17 (which isn't related at all). Faced with a visual distinction between Sc-Y-Lu-Lr-[gap]-La-Ac, and Sc-Y-La-Ac-[gap]-[nothing] + F-Cl-Br-I-At-Ts-[gap]-Lu-Lr, I think the former does better.

I believe points 3 and 4 together address the opposition of R8R, and that points 5 and 6 (perhaps also 7) some way to addressing the opposition of Sandbh.

Merely supporting Sc-Y-Lu as a default does not mean that I wish to force it on WP with no room given to Sc-Y-La. On the contrary, I would support continuing to do what we currently do on the infoboxes, i.e. referring to the block Lu is in as "d-block (sometimes considered f-block)", adding notes to the group 3 assignments of these elements stating that they are under some discussion among scientists, and so on. It merely means that I think the context we are writing in is better served by a Sc-Y-Lu default table with a footnote about Sc-Y-La, than it is by a Sc-Y-La default table with a footnote about Sc-Y-Lu.

• p-block: The last advantage of annexing group 12 to the transition metals, as many texts do, is that the problem of what to call the remaining metals naturally solves itself. They are the "p-block metals". While "post-transition metal" has the problem that Al is arguable, and the other category names aren't really so widespread, "p-block metals" at least unites two common terms: "p-block" and "metal".

This thus neatly divides the metals into four categories: s-block metals (AM + AEM), f-block metals (~ Ln + An), d-block metals (~ TM), and p-block metals (~ PTM). So far, the number of categories has fallen by two.

Now we come to the metalloids and nonmetals. It seems to me rather odd to only use a block division for the metals; it seems to carry a connotation that such a division is not applicable to the nonmetals. This is not true; it's just that most of the nonmetals and metalloids are in the p-block, so we don't get much information out of it. But I think there is a case for more mergers.

• Halogens and noble gases. It seems to me that since the categories are really the intersections of groups 17 and 18 with "nonmetals", it's not completely necessary to actually call them out. It is not clear in the literature whether "halogen" means the whole group or just the category F-Cl-Br-I or maybe F-Cl-Br-I-At. (To put it another way, it is not clear if Ts automatically becomes a halogen, or if it has to pass the bar of actually behaving similarly to the halogens we already know are halogens.) So instead of making "halogen nonmetal" sound like a real term in itself, it seems to me that's it not necessary to have three separate nonmetal categories when two are just calling out common groups.

An advantage is that we then get one single category: there's no need for "other nonmetals", we just have "nonmetals". Including both current reactive nonmetals and noble gases. Yes, the noble gases are maybe somewhat distinct, but we put noble metals with transition metals, so it seems all right to me. The range of behaviour of the TM category from yttrium to gold is quite extraordinarily large already, so this doesn't seem too bad.

We can get away with deleting one more category.

• Metalloids. I would personally favour deleting this category altogether. First of all, there is a sort of inherent contradiction in the name: anything that's not a metal should kind of obviously be a nonmetal. Second of all, IUPAC doesn't seem to like it very much, as Sandbh has noted.

Now, what should we do with the annexed elements? The obvious solution is to take the name seriously and to classify them all as nonmetals. But this raises another question: what exactly is a metal? Here the problem is not so much that the term is not used (it is used very often, including by IUPAC) but that it is used without being clearly defined much.

The IUPAC Gold Book sheds a little bit of light on the situation with its definition of metal-nonmetal transition (or metal-insulator transition) here: "A transition characterized by a sudden change in electrical transport properties (conductivity) due to a reversible change from localized to itinerant behaviour of the electrons." But this is a definition for substances, not for elements. There is no definition of that.

In the absence of this, I feel that due to

WP:OR

it is not a good idea to state exactly which elements are metals and which are not. I am also somewhat in sympathy with this notion: to me it is rather that an element can form a metallic simple substance, and that "is an element a metal" is not a particularly important question to ask. The chemical properties common of metals are not so much defining features, but tend to correlate with the physical ones because easy delocalisation of electrons also tends to imply that they are easily lost. But it's clearly not something universal: germanium doesn't have the physical properties but has some of the chemical properties of a metal (rather weakly expressed, but they're there), whereas tungsten is mostly lacking in the stereotypical high-school metal properties but is physically an excellent metal.

The precise location of the metal-nonmetal line is not agreed on between authors; nonetheless its rough location is pretty commonly agreed. So we can obviously discuss the metal-to-nonmetal trend on the periodic table. But I think it is not a good idea to outright say which elements are metals and which elements are not on WP when there is no clear agreement on that in the literature.

This also has the benefit that instead of the intersections "s-block metal", "p-block metal", and so on, we finally have a complete set of categories that are mentioned by IUPAC in the Red Book and are standard in the literature: "s-block", "p-block", "d-block", and "f-block".

At the level we are looking at, I suggest that this is the most useful presentation for our context. The periodic trend that says that metallicity increases to the left and to the bottom of the periodic table is of course useful to know and can be covered at a general level; but the minutiae of chemical details that are needed to clearly explain why something or another is chosen to be a metal or not are, to my taste, not exactly relevant to something which will be on articles that aren't about the classification issue. At this level, I suggest that only the very basics are needed: the Madelung filling order is among them, as it appears in chemical courses way before the excruciatingly detailed investigations that are needed to decide which of some contentious elements are metals or not, or whether the chemistry merits Sc and Y to be moved (I do not think it does, but you know that already). So I suggest that for the present context, Sc-Y-Lu + blocks alone is enough.

And therefore I propose annexing the metalloid and nonmetal categories altogether to the respective blocks and colouring by blocks alone as follows. Let's call this version DS1A.

s-block

f-block

d-block

p-block

Now, if the voices against blocks alone are too strong, I can offer a compromise that still includes the metal-to-nonmetal trend. This would involve colouring categories as "s-block metal / s-block nonmetal", "p-block metal / p-block nonmetal" etc. But it would force us to make editorial calls on exactly which elements are metals. In the absence of some sort of consensus in the literature, or even a sort of consensus with two major options alone as we have for Sc-Y-La vs Sc-Y-Lu, I feel this would go too far into

WP:OR

and therefore would only go to this reluctantly.

The way I have done it above seems to me to be free of any possible sign of

WP:OR

, appropriate to the introductory level expected of a template that expects to be used in many different contexts, and has the advantage that there are no more "other" non-categories. The only major IUPAC-acknowledged block-related dispute, far from leading to a multitude of different classifications, can be safely listed in a footnote giving the two alternatives.

You'll notice that I don't list the helium saga because IUPAC hasn't acknowledged it officially.

Finally, this category list shows perfect compliance with all seven YBG criteria:

1. Clear. The division is by blocks alone as the only criterion.
2. Unambiguous. Well, as soon as an author has decided on the group 3 composition, the blocks are straightforward even if not often defined properly.
3. Meaningful. As these valence orbitals are the underpinning of about 100% of chemistry, it seems clear that the division has a real meaning.
4. Referenced. Quite clearly so.
5. Specific. Indeed. There are even no "unknown" elements because the superheavies tend to get provisionally assigned to blocks anyway. That's inherent in where they're placed on the table in the first place.
6. Unique. Clearly, the categories are mutually exclusive.
7. Complete. And equally clearly, they are jointly exhaustive.

Moreover, with just four categories, we are free to have a very clear colour-based distinction. As discussed earlier, even the colours used themselves for the blocks have some degree of standardness!

As the icing on the cake, such a "blocks alone" scheme is in fact not something we're making up ourselves, but is in fact extremely common in the Russian-speaking world. It is also the only exhaustive and mutually exclusive scheme that appears in the IUPAC Red Book: "Optionally, the letters s, p, d and f may be used to distinguish different blocks of elements."

Of course, I would support a discussion of categories in the main periodic table article. And of course, you can see that for the one flaw in this (the ongoing group 3 dispute), a long footnote is added.

Finally, I should note that it is not a must for me that we change back to Sc-Y-Lu in order to use such a scheme (although that would naturally be my personal preference). Such a breakdown into blocks alone, plus a similar reciprocal footnote, can be added just as well with a Sc-Y-La format, and may be called version DS1B.

s-block

f-block

d-block

p-block

My preference order is: DS1A > DS1B > Sandbh V5A with PTM changed to other metals and "light nonmetals" changed to other nonmetals > Sandbh V5A with "light nonmetals" changed to other nonmetals > current status quo > others.

@YBG, ComplexRational, DePiep, R8R, Droog Andrey, and Sandbh: Opinions requested. Double sharp (talk) 15:32, 8 October 2020 (UTC)[reply]

Sandbh comments

• From the COPTIC database, only 15% of sources take a "blocks-only" approach.
• "s-block metals" for a unification of the AM and AEM is a good "crisp" idea.
• Extending the block approach to the rest of the periodic table on consistency grounds, when there is no such periodic table colour category consistency in the literature has, as I said, no basis in the literature. I feel this hides knowledge.
• Calling the inner transition metals "f-block metals" is OK by me, as a long as we include the lanthanide and actinide labels in the graphic. As a bonus, f-block metals is shorter.
• Calling the transition metals the "d-block metals" is not OK by me.
• With respect to the p-block, all kinds of hell break out here due to the meeting of the metals and the nonmetals. Getting rid of the metalloids and noble gases, and excluding the halogens, is non-encyclopaedic and, I feel, hides knowledge.
• An encyclopaedia tells the story as it is, as best as it can, regardless of whatever inconsistencies there are in the literature.
• A 4-category block table belongs to our Block (periodic table) article, rather than being the focus of our periodic table FA.

What do we have then? Quite a bit, in my view. YBG, DS and I broadly support an AM-AEM unification. YBG and I support 4+4. DS and I support a division of the reactive nonmetals; R8R previously expressed in-principle support for such a division.

We're circling around the same star, in slightly different orbits. Crudely and broadly, we have:

Metals	Nonmetallic	Nonmetals
• s-block † • Transition • f-block ‡ • Post-transition	• Metalloid	• Unnamed ¶ • Halogen • Noble gas

† similar; soft; single-valent (+1 or +2); sensitive; some sizzle in water
‡ "footnote" metals ^_^
¶ we have or haven't discussed:

Putative names for the group 1 & 14–16 nonmetals

Name	Notes	In the literature?
Biogen		Yes
CHONPS	Stands for carbon-hydrogen-oxygen-nitrogen-phosphorus-sulfur-(selenium)	Yes
Goldilocks or Type G	They have properties that are neither too extreme, nor too weak, but just right to support life as we know it	Not yet
Intermediate		Yes
Light	See note A	A. Yes; relatively the most common B. Found across at least 20 disciplines
Light reactive	Knocks out the helium conundrum	Yes; see also note A
Moderately active	A. Suggested to me by a published chemist, with a reservation about O B. I suggest O can be regarded as an outlier C. A crisp categorisation in terms of the EN, IE and EA table, here.	Note B
Organogen		Yes
Orphan		Yes (popsci)
Other		Yes
Pre-halogen	A crisp neutral descriptive phrase, echoing PTM	Yes, but not in that sense
RAIL	Refractory and interstitial light-life	No

Notes

A. The literature records such terms as (a) "light lanthanoids" and "heavy lanthanoids"; (b) "light actinides" and "heavy actinides"; and (c) "light transition metals" (period 4) and "heavy transition metals" (periods 5 and 6).

The (a) and (b) set features a vertical divide; (c) has a horizontal divide.

Since the "non-halogen non-inert gas" nonmetals span periods akin to the Ln and An, and groups akin to the TM, "light nonmetals" would then refer to the nonmetals in groups 1 and 14-16, with a vertical divide = 16|17, and in periods 1-4, with a horizontal divide = 4|5. Such an approach is consistent with established nomenclature practice.

B. Wulfsberg (2000): "Most of the moderately active metals and nonmetals (the electropositive metals and electronegative nonmetals) are reduced from their oxides…using carbon."

Welcher (2001): "The elements change from active metals to less active metals, to metalloids, to moderately active nonmetals, to very active nonmetals, and to a noble gas."

Perlman (1970): "Between Groups I and VII there are gradations from active metals (Col. I) to less active metals to moderately active nonmetals to volatile nonmetals (halogens Col. VII)."

Sorokhtin at al. (2007): "Nitrogen is a moderately active element, reacting weakly with natural inorganic compounds."

Gelender at al. (1959): "This oxidation may be accomplished by: (a) The use of suitable oxidizing agents for moderately active nonmetals."

Timm (1950): "Oxygen is a moderately active nonmetal and will combine directly with nearly every other element to form an oxide.

Legend 4 (featuring 4+4)

Metal				Metalloid	Nonmetal
s-block	Transition	f-block	Post- transition		Moderately active	Halogen	Noble gas

Table 1: NONMETAL PROPERTIES

Nonmetal	Ionisation energy (kJ/mol)	Electron affinity (eV)	Electro-negativity
Metalloids
B	897	27	2.04
Si	793	134	1.9
Ge	768	119	2.01
As	953	79	2.18
Sb	840	101	2.05
Te	879	190	2.1
Moderately active nonmetals
H	1,318	73	2.2
C	1,093	122	2.55
N	1,407	−0.07	3.04
P	1,018	72	2.19
S	1,006	200	2.58
Se	947	195	2.55
O	1,320	141	3.44
Halogen nonmetals
F	1,687	328	3.98
Cl	1,257	349	3.16
Br	1,146	324	2.96
I	1,015	295	2.66
Noble gases
He	2,372	−50	5.5
Ne	2,088	−120	4.84
Ar	1,521	−96	3.2
Kr	1,351	−60	2.94
Xe	1,170	−80	2.4
Rn	1,037	−70	2.06

Per table 1, what distinguishes the halogens is that they're the only nonmetals each having high values for IE and EA and EN. The noble gases are distinguished by, among other things, not having any EA.

In general, the higher an element's ionisation energy, electron affinity, and electronegativity, the more nonmetallic that element is: Yoder CH, Suydam FH & Snavely FA 1975, Chemistry, 2nd ed, Harcourt Brace Jovanovich, New York, p. 58.
--- Sandbh (talk) 07:25, 9 October 2020 (UTC)[reply]

Shared attributes of the moderately active nonmetals

Here's an update:

The moderately active nonmetals H, C, N, O, P, S, and Se feature a rich array of shared characteristics. Summarising, they are distinguished by their:

1. sub-metallic, coloured or colourless appearance, and brittle comportment if solid;
2. moderate net non-metallic character;
3. covalent or polymeric compounds;
4. prominent biogeochemical roles;
5. proclivity to catenate (form chains or rings);
6. multiple vertical, horizontal and diagonal relationships;
7. uses in combustion and explosives;
8. uses in nerve agents;
9. uses in organocatalysis;
10. interstitial or refractory compounds; and
11. dualistic Jekyll (#4) and Hyde (#7, 8) behaviours, including being unified by their shared attributes despite their diverse individual natures.

10. Capacity to form interstitial or refractory compounds
It was known from an early time (West 1931, p. 121) that light nonmetals, including the metalloids boron and silicon, formed refractory (hard, high-melting) compounds among themselves or

"interstitial" compounds

with some transition metals, often of a similarly refractory nature. It was initially thought that the non-stoichiometry of many of the transition metal compounds suggested the nonmetal atoms were occupying some or all of the interstices in the metallic lattices, without altering the lattice types. The formation of such compounds was then facilitated by the smaller-sized nonmetal atoms and, seemingly, ionization energy values, "sufficiently low to avoid exclusive ionic bond formation" (Glasson & Jayaweera 1968). It is now clear that the lattice types are frequently distorted from those of the host metals (Wulfsberg 2000, p. 791).

The subject compounds include interstitial

sulfides (Ce₂S₃; ~2000 °C). Here, selenium is a borderline interstitial-compound-former (Goldschmidt 1967, p. 43). In the case of the carbides, many thousands of tons of the refractory interstitial compound tungsten carbide (WC) are produced annually around the world and used in cutting tools, industrial machinery, sports equipment, abrasives, surgical equipment, and jewellery. Refractory oxides can be heated to white heat

without melting (Wulfsberg 2000, p. 685). More generally, refractory compounds are used in furnaces, kilns, incinerators, and reactors, and to make crucibles and moulds for casting glass and metals.

In the search to design new superhard materials, there are two main approaches. "In the first, light elements, including boron, carbon, nitrogen and/or oxygen, are combined to form short covalent bonds. In the second, elements with very high densities of valence electrons [i.e. transition metals] are included to ensure that the materials resist being squeezed together. Purely covalent bonding (such as in diamond) is best, and some ionic character is acceptable. However, highly ionic or metallic bonding is the same in all directions and therefore poor at resisting either plastic or elastic shape deformations." (Kaner, Gilman & Tolbert 2005).

Notes

1. (a) The fractions represent the largest amount of hydrogen that can be accommodated without distorting the lattice structures of the host metals (Wiberg 2001, p. 258). (b) In palladium hydride, the lattice is not altered and is never stoichiometric, with no more than 0.8 hydrogen atoms per palladium atom (Wulfsberg 2000, p. 792). (c) Niobium forms a series of non-stoichiometric hydrides NbH_x (0 < x ≤ 1) which, at low hydrogen content, retain its body-centred cubic metallic structure (Housecroft & Constable 2010, p. 703).

2. The binary compound 4

ZrC

has the highest recorded melting point of 4215 °C (MacKay, MacKay & Henderson 2002, p. 314)

3. (a) A thin film of TiN was chilled to near absolute zero, converting it into the first known superinsulator (cf. superconductor), with its resistance suddenly increasing by a factor of 100,000 (Vinokur et al. 2008). (b) The Boeing company (2010) has a patent for the use of zirconium nitride as a hydrogen peroxide fuel tank liner for rockets and aircraft.

4. Highest known melting point for an oxide

5. Listed as a ceramic material (O’Bannon 2002)

References

• Glasson, D.R., Jayaweera, S.A.A. Formation and reactivity of nitrides I. Review and introduction. J. Appl. Chem., 18: 65−77 (1968)
• Goldschmidt, H.J: Interstitial alloys, Butterworths, London (1967)
• Kaner, R.B. Gilman, J.J, Tolbert, S.H. Designing superhard materials. Science. 308, 1268-1269 (2005)
• West, C.J.: A Survey of American Chemistry, National Research Council (U.S.). Division of Chemistry and Chemical Technology, Chemical Catalog Company, New York (1931)
• Wulfsberg, G.: Inorganic chemistry. University Science Books. Sausalito, CA (2000).

--- Sandbh (talk) 06:04, 10 October 2020 (UTC)[reply]

R8R comments

I think Double sharp’s DS1 proposal has its merit. I am afraid to think, however, that we lose some important knowledge in this scheme. Transition metals and noble gases, for example, are of superb importance and they don’t clash with anything. The metalloid category is fuzzy indeed, but we have a good understanding where it is located in the PT. As an encyclopedia writer, I feel we’re losing out without such categories.

I think Sandbh’s proposal is rather inconsistent. While Double sharp suggested a proposal, in which all categories were chosen based on the same principle (PT block), Sandbh’s table composed mere blocks with actual chemical categories. I don’t believe this is good, and my feeling is strong about this. To mirror Sandbh’s words, if it’s not okay to call transition metals “d-block metals” (something Double sharp never proposed in the first place: he went for “d-block”) then by applying the same principle, it is not okay to call alkali and alkaline earth metals “s-block metals”. In both cases, chemical names are known very well. I could see us use DS1 even if I think we’d lose lose out a bit by doing that; I can’t see us combine “s-block metals” and “transition metals.”

Our goal is to reflect common knowledge. We are losing out by ignoring those two well-known names and going for generic “s-block metals,” especially if this is inconsistent with other names. The same goes for “f-block metals”.

For an encyclopedia writer, reactive nonmetals leave room for discussion. The same can’t be said of either the s-block or the f-block, where we have four well-known and IUPAC-approved names.—R8R (talk) 11:15, 10 October 2020 (UTC)[reply]

@R8R: Thank you for your comment. I would like to wait on a reply before the ANI thread reaches a conclusion and we know how the discussion should proceed from here on, but I want to make it clear that I have seen it and will think about it. ^_^ Double sharp (talk) 12:41, 10 October 2020 (UTC)[reply]

I'd like to continue the discussion regardless of ANI. I feel stressed by ANI. In contrast, it's good to be able to discuss matters here amongst knowledgeable colleagues. YMMV however.

I have no particular stake in retaining "s-block", or "f-block metals". I supported the "s-block/s-block metal" suggestion since a merge of the AM and AEM has good support from three of us. @R8R: Since all of the elements in the d-block, as far as we know, are metals, I treated the terms "d-block" and "d-block metals" interchangeably. So, I'm happy to keep "transition metals" even though that term is neither approved nor endorsed by IUPAC! So much for consistency! ^_^

Like the metalloids, the orphan nonmetal category can be fuzzy, but we have a good understanding of where it is located in the PT.

Regarding consistency: I submit there is no such thing in the literature. As I see it, we are once again seeking to hold ourselves to a standard with no basis in encyclopaedic terms. I say "we" in the sense of our project, absent of informal consensus. @Double sharp:, as you wisely observed, if one wants to write a book one can "consistently" knock one's self out in any way one likes; in an encyclopedia this is unjustified and uncalled for.

There is no need to lose out on AE and AEM. I have previously suggested adding a note to the legend saying that in the unified colour category, group 1 are the AE and group 2 are AEM. Nothing is lost.

I have no stake in f-block metals. I was trying to retain the best parts of Double sharp's suggestion. I'm not sure what the issue is with f-block metals, in any event. It doesn't hide anything. The Ln and An labels can be retained. As noted, there is no consistency in the literature on these matters and I'm puzzled as to the WP- or encyclopaedic-basis for raising a concern about this. Even IUPAC, for once, recognises the optional use of the letters s, p, d or f to distinguish blocks.

The term "reactive nonmetals" has little support in the literature (ngram = ~1). It conceals a relatively extensive amount of knowledge—included a marked distinction between the halogens F, Cl, Br, and I(At), and the orphan nonmetals—rather than reflects knowledge, and is non-encyclopaedic from that perspective.

For the category names of s-block or f-block metals, nothing would be lost. The four approved IUPAC names will continue to appear in the graphic. Knowledge would be added rather than concealed via "s-block" and "f-block"; reader interest has the potential to be piqued, in the best tradition of any encyclopaedia.

The Red Book says, "the elements of groups 3–12 are the d-block elements. These elements are also commonly referred to as the transition elements, though the elements of group 12 are not always included; the f-block elements are sometimes referred to as the inner transition elements." Therefore, "transition elements" and "inner transition elements" are acknowledged by IUPAC. There is no acknowledgement for a name for the s-block metals.

I have not made a comment on reactive nonmetals; I merely said that there is room for discussion. This is not something I'd want to discuss at the present moment.

The best part of Double sharp's suggestion is that it only features blocks, leaving aside all questions like what is a metal, not to mention which nonmetals are very reactive and which are merely moderately nonreactive. Back when I went to school, the periodic tables in both the chemistry classroom and the physics classroom featured only blocks. Having three categories in the s-block, one in the f-block, three or four in the d-block, and five in the p-block defeats the entire point of DS's suggestion.

Let's try and mirror the note argument. Say, we'll leave the AM and AEM categories and add a note mentioning "very reactive metals" or any other name suggested below for it. Would that note make much sense? I'd say not, and as such, it seems clear AM and AEM are more important, and that's what we should strive to reflect as an encyclopedia.--R8R (talk) 14:17, 11 October 2020 (UTC)[reply]

@R8R: Thanks. I've seen this too. ^_^ Double sharp (talk) 18:42, 11 October 2020 (UTC)[reply]

The Red Book + blocks

Thank you R8R. Good to hear from you.

We have chosen to ignore the Red Book, since we use "transition metals" yet that is neither endorsed, recognised or approved by IUAPC. Rather, "transition metals" is an adaptation. The IUPAC Red Book says, "Optionally, the letters s, p, d and f may be used to distinguish different blocks of elements." In the same way, "s-block metals" is an adaptation. Mostly this question has become superseded since, according to the literature, the preferred term is "Early main group metals", per the twenty-five quotes listed below.

We have chosen to further ignore the Red Book by including metalloids but not including rare earth metals—an IUPAC-approved term—and despite the popularity of this term or variants in the literature, being ×2.5 as popular as "noble gases", for example.

After IUPAC (1970) recommended abandoning the term metalloid, its use increased dramatically. Google's Ngram Viewer showed a ×4 increase in the use of the word 'metalloid' (as compared to 'semimetal') in the American English corpus from 1972 to 1983. There was a ×6 increase in the British English corpus from 1976 to 1983. As at 2011, the difference in usage across the English corpus was around 4:1 in favour of 'metalloid'.

I suggest The Red Book is a consideration but as well being outdated and unclear in itself, parts of it are widely ignored by the chemistry establishment.

On blocks, the COPTIC database shows that only 15% of textbooks show just the blocks; 35% show metals-metalloids-nonmetals; 50% show categories. That is why I'm not in favour of limiting our table to just blocks. It's not reflective of the literature, and is non-encyclopedic since such an approach hides knowledge—knowledge which is easily displayed in a graphic.

I don't understand the mirror-example basis for adding a note to the legend saying the AE and AEM are very reactive. We don't add a note saying the metalloids are chemically weak nonmetals, or that the halogens are very reactive nonmetals. Or that while we show astatine as post-transition metal, it is a halogen according to the Red Book.

Since the PT graphic appears in the lede, it is more of a high-level summary. As such, YBG's aim for 7±2 is a relevant consideration. In this context, I suggest the following quotes from the literature are relevant too:

• "The chemistry of these elements [AEM] resembles that of the IA metals to a large degree. (Hamm 1969, p. 369)"
• "The difference between the Group I and Group II elements (except Be) is more of degree than kind." (Choppin and Russell 1972, p. 334)
• "Alkali (Group IA) and alkaline earth metals (Group IIA) share a host of common physicochemical attributes." (Arevalo 2016)

Also relevant, as noted, the chemists refer to the group 1 and 2 metals as early main group metals, which is precisely and concisely captures the alkali metals and alkaline earth metals, and is more accurate than either individual term, neither Be nor Mg being AE for example.

As an encyclopedia, we can get closer to 7±2 AND we can retain the AM and AEM by way of adding a note to the legend. There is no need to settle for an "either (x) or (y) but not both" outcome. I have tried to show this in the accompanying basic value template (from Hampden-Turner’s (1994) dilemma theory). --- Sandbh (talk) 03:04, 12 October 2020 (UTC)[reply]

I somewhat agree that we shouldn't use a category just because the Red Book includes it. Still, I consider such an inclusion an important argument for its usage. I recall you said that the Red Book mentioned the "noble metals" as a way to support your argument back then (it doesn't, but that's beside the point). I feel it would be inconsistent to agree with it on one occasion and not agree on another.

I feel that the COPTIC argument, as it is stated, is incomplete. What kind of categories does it primarily use? Bocks, after all, are categories, too, or is it blocks vs. metal-nonmetal vs. anything else? What info you have given is not sufficient to make an argument on its own, though maybe there is more to it. By any chance, do those categories include alkali metals and alkaline earth metals?

That's precisely it. It doesn't make much sense to add the reactive note if such a category is not present, but it does make sense to include a AM and AEM note if these categories aren't present. That is because AM and AEM categories are encyclopedically important, and "reactive metals" are not nearly as much. (The astatine argument is unclear to me and seems to be an argument against notes in general.)

It doesn't matter if the categories are similar. What matters is that any common category is much less common than either AM or AEM. We should reflect sources rather than make a perfect categorization.

I tried to see how common the term "early main group metals" really is, and Ngram tells me this: Ngrams not found: early main group metals.

7±2 has nothing to do with being an encyclopedia. It is a good rule, but it has nothing to do with writing an encyclopedia, and it's only approximate anyway. I'd much rather sacrifice the reactive nonmetal division because while "reactive nonmetal" is not a common term, neither is "other nonmetal" or whatever it might be.

We need to follow sources, not try to create a better categorization than most sources would do. "Alkali metal" is a well-established compound noun; "early main group metals" is not.--R8R (talk) 19:45, 12 October 2020 (UTC)[reply]

@R8R: Since IUPAC recommendations have a notable record of being ignored I’m not sure why (necessarily) a category recognised by IUPAC counts as being an important argument for its usage absent of other considerations. In any event I'm supporting the inclusion of the AM and AEM as notes to the legend, as a synergistic outcome. On noble metals I never said the Red Book included them. If I did then I’d be fascinated to see where I did. If noble metals had indeed been included in the Red Book, I would’ve been trumpeting that to the world, which I didn’t, since it isn't.

The COPTIC database is based on the “lede” periodic tables in 62 more recent chemistry textbooks. Only 15% showed blocks only; the rest showed metals-metalloids-nonmetals and/or sundry categories. About 8%[!] showed AM and AEM. Your ngram experience is the same as mine. That said, I provided 25 quotations (1978−2020) for "early main group metals"from the literature, and there is a lot to them as it turns out. As Double sharp helpfully observed there was never a historical effort to ensure equal support for the use of all categories. Instead, there was the usual iterative interaction between science and theory or observation, and classification science. Early classification schemes get superseded by “better” schemes, in a stop-start, in whole or in part, in a haphazard fashion, across different fields. Hence there is no perfect scheme, as you said. All we can strive for is an encyclopaedic representative scheme.

7±2 is a good aspiration to keep in mind when trying to break down a complicated concept into digestible reading and learning chunks. I sometimes do that here with a big bullet point list. I break the list up into units of five bullet points. This kind of “conceptual chunking” approach is highly relevant in writing for an encyclopaedia.

We need to follow the sources in an encyclopaedic manner. “Encyclopedia” means “complete instruction" or "complete knowledge”. They do this by drawing on the literature and applying judgement as to the best way depict or attain complete knowledge. The founders of the original WP PT categories attempted to do the same thing. Sandbh (talk) 07:51, 13 October 2020 (UTC)[reply]

@Sandbh: That's not exactly what I said. I said that historically, the categories were never intended to be mutually exclusive and jointly exhaustive; they were only intended to group together similar elements. I then said that it hence isn't a surprise that trying to make them so inevitably leads to either "other" leftover categories or categories without significant name recognition. Therefore I submit that there is no point in striving for an "encyclopaedic representative scheme" when many sources seem uninterested in creating any such scheme at all. They seem only interested in creating a bunch of categories without paying any attention to how good the boundaries are. In that situation, any complete scheme we create at all cannot possibly be representative.

I feel that it is not correct to apply such judgement to find the "best way" to depict or attain complete knowledge. That is something that should be done only if one has one's educator hat on, to take a leaf out of User:EdChem's book. It's a matter of applying judgement as to what the relevant literature as a whole is saying, even if we think that that is not complete knowledge. Double sharp (talk) 09:39, 13 October 2020 (UTC)[reply]

@Double sharp: I tend to agree. When I have read authors writing about their category decisions they acknowledge the fuzzy boundaries in some fashion, usually explaining the reasons for this or that decision, sometimes noting differences of opinion, and then they move on. The schemes involved are representative to the extent that each supports the author in setting out the subject matter of their book. That’s all. Of course, they do pay attention to the boundaries only to the extent they feel it is necessary to do so. That goes back to the classic line about not losing sleep about the hard cases as long as the scheme provides an economy of description and is beneficial to the structuring of knowledge and our understanding.

A good example of an encyclopaedic PT is the Encyclopedia Britannica colour category periodic table. Here we have a table that matches ours mostly, except it notably divides the nonmetals into other nonmetals (inc. mushing in the metalloids); halogens; and NG. I looked into the history of the EB table; it predates the WP colour category table! That’s what I call an encyclopaedic PT! Good enough for them; should be good enough for WP. Note theirs is better than ours in that it includes the rare earths as a category, with the Ln mentioned in the legend as a subset of the RE, consistent with IUPAC (although IUPAC refer to REM rather than REE, but TM as TE—go figure).

In any event, with the gold standard delineation of the metalloids, there are no overlaps worth worrying about other than what we say about atypicality at the boundaries in each category, in the four WP articles I mentioned. To the L of the metalloids are the AM, AEM (separate or merged), TM, Ln/An, and “fusible metals” (another term found in the literature); to the R are the CHONPS or whatever nonmetals, halogens, and NG. That’s where the literature overall has settled down. I’ve been watching more recent mentions of the metalloids and my impression is that they are more consistently than ever converging on the gang of six.

BTW any group 1 and 2 merge should be first tested via an RFC on the PT talk page. I don’t believe that would be required for a split of the reactive nonmetals given we have had such a split for most of the history of our PT colour categories. We could not think of something “better” than other nonmetals. Well, it turns out there is such a literature-based term in the form of moderately active nonmetals, as suggested to me by an off-list chemist when I asked him how he felt about light nonmetals. Sandbh (talk) 10:36, 13 October 2020 (UTC)[reply]

@Sandbh: I feel that the applicability of this argumentation is somewhat dependent on where one stands. I feel there is a sensible inconsistency between these two phrases, which come from the same paragraph: "since IUPAC recommendations have a notable record of being ignored I’m not sure why (necessarily) a category recognised by IUPAC counts as being an important argument for its usage absent of other considerations" and "If noble metals had indeed been included in the Red Book, I would’ve been trumpeting that to the world." Inclusion in the Red Book should either be consistently a strong argument or consistently not be a strong argument (I wouldn't presume you were talking about trumpeting what you did not consider a strong argument). My own take is that it's a strong argument, even though it's not decisive.

The phrase about the noble metals is this (from #About halogens): "no mention of noble metals, a popular and IUPAC-endorsed name." I would expect that an endorsement from IUPAC should be stated in the Red Book of all places, so that's why I looked there. If you meant a different endorsement, please let me know.

Okay, that's really interesting. 15% showed blocks and 8% showed AM and AEM. What did the other 77% show? Could it be that most of these sources merely showed metals, and only metals? I feel that what we know so far is not enough to make a solid argument based on this because we still don't know what exactly the majority of the sources in that database says, but this argument could potentially be expanded upon.

"7±2 is a good aspiration" -- yes, and let's leave it at that. I was merely doubting this particular phrase: "As an encyclopedia, we can get closer to 7±2." Indeed we can, but we simply can get closer to seven plus-or-minus two by ourselves, not as an encyclopedia. I feel that as an encyclopedia, we may have as many categories as we should; seven plus-or-minus two is a good consideration but not an encyclopedic one. I'm not rejecting it, merely clarifying what exactly words are worth here.

"“Encyclopedia” means “complete instruction" or "complete knowledge”" I actually never knew if that was the case. Our encyclopedia article says, "The word encyclopedia (encyclo|pedia) comes from the Koine Greek ἐγκύκλιος παιδεία, transliterated enkyklios paedia, meaning "general education"" -- that's not quite the same, wouldn't you agree? (I remember reading that Jimbo Wales thinks that a very rare point of view, however correct, should not be featured in Wikipedia, and that was the consideration that raised my suspicion about that etymology.) Anyway, we can always give more knowledge in the article text, we can describe both "pnictogen" and "metalloid" even if the two overlap. We don't need to describe both in our general PT.

"The founders of the original WP PT categories attempted to do the same thing." -- I can't help but think this is a very retrospect statement. In what way could one know that? Those founders came up with "alkali metals", "alkaline earth metals", "lanthanides", and "actinides," after all, so the argument could very well be in favor of keeping those categories.--R8R (talk) 11:37, 17 October 2020 (UTC)[reply]

4+4 options

All category names are found in the literature. How do these options appear?

Legends 5 to 8

Metals				Metalloid	Nonmetals
Pre- transition	Transition	Inner transition	Post- transition		Moderately active	Halogen	Noble gas

Legend 6

Metals				Metalloid	Nonmetals
Pre- transition	Transition	Inner transition	Poor		Moderately active	Halogen	Noble gas

Legend 7

Metals				Metalloid	Nonmetals
Highly active	Transition	Inner transition	Poor		Moderately active	Halogen	Noble gas

Legend 8

Metals				Nonmetals
Light	Transition	Inner transition	Poor	Metalloid	Moderately active	Halogen	Noble gas

As noted, the moderately active nonmetal category name was suggested to me by a non-WP chemist with several publications, in response to a PM I sent them asking how they felt about the term "light nonmetals". ('Not happy' was the start of their reply).

In all four cases, the labels Lanthanide and Actinide are included in the graphic, adjacent to the start of the 4f row and 5f row, respectively. One note is added under the legend, referring to group 1 as the alkali metals and group 2 as AEM.

Active metals: 16 of the top 20 places in the Standard electrode potential (data page) league ladder for metals are occupied by group 1 or 2 metals. The interlopers are Pr, Er, Eu and Ho, representing the usual boundary overlap.

Light metals: this includes aluminium, per Deming (1940) and Cox (2004). Yes, there are overlaps at the boundaries, once again, since Sc, Y and Ti can be regarded as light metals, too. They are, however, widely regarded as TM. Ra, too can be regarded as a heavy metal.

Bear in mind when considering these options that there are:

• no perfect categorisation schemes;
• only schemes that are more or less encyclopaedic in nature.

--- Sandbh (talk) 02:18, 11 October 2020 (UTC)[reply]

Legend 9 (for the 19^th century)

Could be a bit too radical? It's been known since at least 1894 (yep, that's the 19th century; and here we are in the 21st) that metalloids have a predominantly nonmetallic chemistry. Sandbh (talk) 05:34, 11 October 2020 (UTC)[reply]

Metals				Nonmetals
Light	Transition	Inner transition	Poor	Metalloid	Moderately active	Halogen	Noble gas

Legend 10 (yes, A & A metals is in the literature)

Metals				Nonmetals
Alkali and alkaline	Transition	Inner transition	Poor	Metalloid	Moderately active	Halogen	Noble gas

--- Sandbh (talk) 06:47, 11 October 2020 (UTC)[reply]

Legend 11: Early main group metals

Metals				Nonmetals
Early main group	Transition	Inner transition	Poor	Metalloid	Moderately active	Halogen	Noble gas

Legend 11a

Metals				Metalloid	Nonmetals
Early main group	Transition	Inner transition	Poor		Moderately active	Halogen	Noble gas

Legend 11b

Metals				Metalloid	Nonmetals
Early main group	Transition	Inner transition	Post- transition		Moderately active	Halogen	Noble gas

There it is, this is what chemists refer to the group 1–2 metals as:

1. "The lightest metal lithium (in [LiCH₃]₄) and the heaviest natural metal uranium (in U₆O₄(OH)₄(SO₄)₆) undergo metal-metal interactions. The number of compounds with metal-metal bonds formed by the metals lying between these two extremes varies; a maximum occurs in the middle of the transition metal series, and that is where the main emphasis of this article lies. The early main group metals, and the lanthanide form a few compounds of this type, while the post-transition elements form many; combination with transition metals provides a means of forming stable metal-metal bonds for all metallic elements."(1978)
   doi:10.1002/anie.197803793
2. "As small-volume cationic charge centers and as a source of unoccupied valence orbitals, the early main group metals have a well-documented but remarkable organometallic chemistry." (1990)
   doi:10.1021/ja00162a057
3. "The hope is to further elucidate the nature of these bonds between p-block metals and early-main-group metals and to assess the structural trends within these compounds." (1991)
   doi:10.1002/anie.199114591
4. "Recently we have explored the bonding between early main group metals M (alkali or alkaline earth metals) and heavy p-block metals E such as In, T1 (group 3), Sn, Pb (group 4), and Sb, Bi (group 5)." (1992)
   doi:10.1002/anie.199212261
5. "carbonyl derivatives of the early Main Group metals are rare and elusive species" (Downs 1993, p. 215)
6. "In addition, this versatile ligand has been shown capable of bonding to the early main-group metals through N…" (1995)
   doi:10.1039/DT9950003139
7. "Secondly, the use of phosphorus-carbon ylides (1, where X = CH,) as neutral donors to early main group metals is only a small conceptual step from the use of…" (1995)
   doi:10.1002/anie.199504781
8. "…especially emphasizing bonds between transition metals and more electropositive (early) main group metals…" (2000)
   doi:10.1016/S0022-328X(00)00279-5
9. "Three‐center, two‐electron bonds involving hydrogen as a bridging atom are a common feature in the chemistry of early main group metals." (2001)
10. "Predictions as to metals with the unfilled 3d shell and early main group metals having no d electrons are not so unambiguous." (2004)
    doi:10.1007/s11172-005-0018-9
11. "…has been incorporated into complexes with early-main-group metals…" (2006)
    doi:10.1021/ic060603x
12. "Complexes of the early-main-group metals are only known as polymeric salts [M(NH₂)x]" (2007)
    doi:10.1021/ic701479r
13. "This paramagnetic ligand can be stabilized through chelation, eg, to early main-group metals." (2008)
    doi:10.1021/ic702435e
14. "Presumably, this process will occur for any ion with a reduction potential more positive than that of iron and hence gives access to many late transition metals and early main group metals." (2008)
    doi:10.1021/la8006734
15. "This paramagnetic ligand can be sthbilized through chelation, e.g. to early main-group metals (Canadian Journal of Chemistry 2009, p. 461)
16. "This can to some extent be seen as a result of the greater degree of covalency involved in metal–ligand bonding as compared to more electropositive early main group metals (resonance form B, Scheme 1)." (2010)
    doi:10.1002/chem.201000656
17. Molecular early main group metal hydrides: synthetic challenge, structures and applications (2012)
    doi:10.1039/c2cc33478j
18. "Thus, the synthesis of gallium–gallium multiple bonds, stable chromium compounds with fivefold bonding between the two chromium centers, the unexpected coordination of early main group metals with the f-elements…" (2012)
    doi:10.1039/C2CS15343B
19. Early main group metal catalysis: how important is the metal? (2015)
    doi:10.1002/anie.201408814
20. "Recent years have seen a renaissance in the field of early main group metal chemistry. Breakthroughs were achieved in the isolation of complexes with metals in a low oxidation state (MgI, CaI), “heavy” Grignard reagents have been isolated and characterized (RCaI), the chemistry of strong mixed-metal bases and TURBO Grignards was further developed, and highly reactive heavier alkaline-earth metal benzyl, allyl and hydride reagents have been isolated. Apart from applications in classical synthetic chemistry, early main group metals are increasingly topical in areas varying from catalysis to new materials and hydrogen storage." (2018)
    doi:10.1039/C8DT90148A
21. "The potential application of early main group metals as catalysts has remained a widely underexplored research field, despite the apparent ecological and economic benefits." (2018)
    doi:10.1039/C8RA04481C
22. Early main group metal catalysts for imine hydrosilylation (2019)
    doi:10.1002/chem.201904148
23. Introduction to early main group organometallic chemistry and catalysis: "This short summary of working principles in catalysis is followed by a discussion on the mechanism of substrate activation by early main group metals… The organometallic chemistry of the highly electropositive early main group metals could not have started without the isolation of these elements in the metallic state." (2019)
    doi:10.1002/9783527818020.ch1
24. Early Main Group Metal Catalysis gives a comprehensive overview of catalytic reactions in the presence of group 1 and group 2 metals (2020)
25. "In general, early transition metal compounds, lanthanides, and early main group metals all are strongly oxophilic… (2020)
    doi:10.1002/9783527818020.ch8

Precise. Doesn't take up too much room. --- Sandbh (talk) 13:12, 11 October 2020 (UTC)[reply]

Legend 11c

Metals				Metalloid	Nonmetals
Early main group	Transition	Inner transition	Post- transition		Biogen	Halogen	Noble gas

There is an interesting Russian connection here (#9):

1. "Organogens - Oxygen, azote, hydrogen, carbon…Sulphuroids. - Sulphur, selenium, phosphorus" (Hoefer 1849, p. 40)
2. "…and are hence called organogens (generators of organic bodies). RETROSPECT OF THE ORGANOGENS (OXYGEN, HYDROGEN, NITROGEN, AND CARBON)" (Stöckhardt 1853, p. 113)
3. "They [C, H, O] are the organogens, without which organization can not exist." (Gatchell 1869, p. 339)
4. Introduction to crystal chemistry, book 2, Moscow University Publishing House (Bakii 1954, p. 458): Treats all the nonmetals, bar the noble gases, as organogen elements i.e. B, C, N, P, O, S, Se, H, F, Cl, Br, I.
5. "There is a considerable variation in the content of the organogens (Ca, K, P, S) and biohalogens (Na, Cl and excess S) in the ash of the discarded plant organs." (Academy of Sciences of the U.S.S.R 1964, p. 157)
6. "The characteristic feature of the litter fall in deciduous forests is the high concentration of the main organogens (Ca + K + P + S)." (Rodin 1968, p. 151)
7. "Organogens should be singled out and subdivided into: (a) absolute organogens without which the existence of organisms is utterly impossible (hydrogen, carbon, oxygen, nitrogen, phosphorus, sulphur, potassium, magnesium)…" (Lapo 1982, p. 93)
8. "The highest selenium content, in some cases exceeding 1 mg/kg, has been found in organogenic soil." (Ylaranta 1988)
9. "…all Russians are selenium-deficient; for this reason, the Chief Sanitarian of Russia G. G. Onishchenko signed in 2000 the Order On Correction of the Quality of Potable Water for the Content of Biogenic Elements[3], including selenium. (Russian Journal of Physical Chemistry, vol. 78, 2004, p. 1980)
10. "Microbes and environment environmental conditions such as temperature, light, nutrition, organogens (C, N, P, S, H, O)." (Rao 2007, p. 27)
11. "It is believed that only certain non-metals C, N, O, S and Se are able to create stable polymeric structures in normal conditions of contemporary environment (Skalny 2011, Bioelementology as an interdisciplinary integrative approach in life sciences: Terminology, classification, perspectives)
    doi:10.1016/j.jtemb.2010.10.005
12. "It can be seen that most of the essential elements (including organogens) are located in the first few periods of the Periodic Table" (Georgievskii et al. 2013, p. 16)
13. "Biogenic nanoparticles of elemental selenium: Synthesis, characterization and relevance in wastewater treatment" (Jain 2015)
14. "Production, recovery and reuse of biogenic elemental selenium" (Staicu et al. 205)
    doi:10.1007/s10311-015-0492-8
15. "In roots [the] difference in quantity of organogens and halogens is insignificant – 2.03 and 2.04 mg-eq …(2018)
    doi:10.30850 / vrsn / 2018/6 / 28-29
    . Comment: Note the distinction between organogens and halogens.
16. "The use of iron electrode at a current density of 300 mA allowed for binding over 96% of the biogenic elemental selenium nanoparticle release from effluent to form stable iron-selenium complex sediments with a reticular structure." (Nancharaiah et al. 2019, p. 122)

--- Sandbh (talk) 03:04, 12 October 2020 (UTC)[reply]

Droog Andrey's comments

Vote for DS1A for obvious reasons. Droog Andrey (talk) 21:56, 12 October 2020 (UTC)[reply]

@

WP:ANI thread – should come up soon (but am busy this week). My apologies if this means you may need to !vote again later on the same thing – I am not 100% clear on the protocols. But your support means a lot to me. ^_^ Double sharp (talk) 22:22, 12 October 2020 (UTC)[reply

]

The Halogens question, again

Again: where or how has it been established that the group halogens is the same as the category "halogens", proposed in these settings? AFAIK, At has not been reassigned convincingly. -DePiep (talk) 20:53, 11 October 2020 (UTC)[reply]

Despretz's natural classification (1829–1830)

Wow, how close did he get to DIM? Sandbh (talk) 23:53, 11 October 2020 (UTC)[reply]

Famille
1	Chloroïdes	Cl, Br, F, I
2	Sulfuroïdes	S, Se, Te
3	Carbonoïdes	C, B, Si
4	Azotoïdes	N,P,As
5	Chromoïdes	Cr, W, Mo, Columbium; + Ti
6	Stannoïdes	Sn, Sb, Os
7	Auroïdes	AU, Ir
8	Platinoïdes	Pt, Rh
9	Argyrodes	Ag, Hg, Pd
10	Cuproïdes	Cu, Pb, Cd, Bi
11	[no name]	Fe, Co, Ni, Zn + Mn, U, Ce
12	AIuminoïdes	AI, Be, Y, Zr
13	Baroïdes	Mg, Ca, Sr, Ba
14	Potassoïdes	Li, Na, K

1−4 Nonmetals
5   Intermediate group
6−14 Metals

• Bertomeu-Sánchez, J. R., Garcia-Belmar, A., & Bensaude-Vincent, B. (2002). Looking for an order of things: Textbooks and chemical classifications in nineteenth century France. Ambix, 49(3), 227–250.
  doi:10.1179/amb.2002.49.3.227

Legend 12 (with blocks)

Since there is some interest in showing these too.

Metals				Nonmetals
1–2	3–11	Between 3 and 4	12–17	13–16	1, 13–16	17	18
Early main group	Transition	Inner transition	Post transition	Metalloid	Moderately active	Halogen	Noble gas
s	d	f	d-p	p	s, p	p	s, p
Hyper	(a) Hyper (b) Working (c) High society	Hyper	Poor		Respectable	Psycho	Cup o' tea

Out of interest only, I added alt-names. Now with group ranges, too. Sandbh (talk) 06:40, 15 October 2020 (UTC)[reply]

I have corrected this legend to reflect that hydrogen and helium are s-block elements. Feel free to revert me but please have this consideration in mind.--R8R (talk) 11:44, 17 October 2020 (UTC)[reply]

Legend 13 (Blocks up front)

In this arrangement, per Double sharp, only the blocks are coloured. Helium stays over neon and will therefore show as s-block. The metallicity categories are retained but instead delineated via unnamed dividing lines as per my earlier 16DL post. The category names are situated above or below each dividing line, as appropriate, depending on design considerations.

s-block	d-block	f-block	p-block
CHONPS nonmetal Alkali metals Alkaline earth metals	Transition metals Post-transition metals	Lanthanides Actinides	Post-transition metals Metalloids CHONPS nonmetals Halogen nonmetals Noble gases

Updated for H in the s-block per DS observation, below. Sandbh (talk) 21:46, 15 October 2020 (UTC)[reply]

There is a reduction in the number coloured regions from ten to four, per YBG. The AM and AEM are retained per R8R.

I do worry that giving the blocks so much prominence is not reflected in the literature, per the COPTIC database, but there it is. There is also the lack of any agreed definition of what a block is (other than in an idealised sense) and which elements belong to which block at the boundaries.

The only notes needed in the resulting compact legend are the two IUPAC ones as suggested by Double sharp re group 3, and the PTM. Sandbh (talk) 09:58, 15 October 2020 (UTC)[reply]

@Sandbh: I'll post my explicit proposal in a few days (exact date depending on how busy I end up being), but this is indeed getting closer to what I would like. However, I would not give explicit categories because they don't totally match the blocks (H and He are not alkali and alkaline earth metals) and because if you don't colour things in by categories, and are no longer forced into the not-really-achievable goal of mutual exclusivity and joint exhaustivity, then it suddenly becomes difficult to justify why "chalcogens" is less worthy of inclusion than "CHNOPS nonmetals". That would leave a lot of possible categories and I feel that for simplicity it's better to discuss these only when more detail is needed than a PT template. So, in the PT article, I'd be happy to discuss a whole range of categories, including both post-transition metals (and the other names for that bunch) and pnictogens even though they can overlap. I just wouldn't want to overcomplicate the templates and infoboxes.

Also: although there is so far no universally agreed definition of what a block is indeed, AFAICS there is actually no dispute about block placements except for the elements caught up in the group 3 dispute. Apart from WebElements everyone seems to agree that helium is an s element even if most people still do place it over the p element neon. If you have any sources (hopefully within, say, the last 60 years or so) that give unusual block classifications outside La-Ac and Lu-Lr, and do so as if they're explaining something standard rather than going out of their way to propose something new, then please do share them with me. ^_^ Double sharp (talk) 10:37, 15 October 2020 (UTC)[reply]

On the periodic table article more generally

I admit that I haven't read all of the above. I am aware of the La v Lu and related debates in the literature and here, and also on the style of colouring the PT on WP. I have also looked through our article on the periodic table, and I am wondering if the debates here are the most important, or whether they go to the issues from the perspective of encyclopaedic content. We are writing for the average of 30,000+ page viewers per day, most of whom will not be chemists with broad knowledge of the topic. Some examples:

Overview – the first section after the lede

I invite you all to stop for a moment and think about what a non-chemist needs to know in the overview of the PT at the start of our article. If you don't remember what is in our article, all the better. I suggest stopping to jot down a few points. If you were asked by someone about the PT, someone with little knowledge, what would you tell them?

Ok, here is the Overview we give. In sequence, it says:

1. Below is a widely-used layout but there are others discussed later
2. 18 column PT provided
3. Every element has a Z giving the number of proton, followed by a note about Z = 0 for neutronium – which isn't on this PT and having mentioned only protons
4. A section about differing neutrons and isotopes – which are not separated on the PT – and going on to atomic masses of of most stable of the non-stable isotopes in parentheses
5. Listed in order of increasing Z. Rows/periods when a new electron shell has its first electron, columns / groups by electron configuration.
6. "elements with the same number of electrons in a particular subshell fall into the same columns (e.g. oxygen and selenium are in the same column because they both have four electrons in the outermost p-subshell)"
7. "Elements with similar chemical properties generally fall into the same group in the periodic table, although in the f-block, and to some respect in the d-block, the elements in the same period tend to have similar properties, as well"
8. "Thus, it is relatively easy to predict the chemical properties of an element if one knows the properties of the elements around it"
9. 118 confirmed elements, most recent discoveries confirmed in December 2015 and names / symbols in November 2016 (Nh, Mc, Ts, Og)
10. first 94 elements occur naturally (83 are primordial and 11 occur only in decay chains of primordial elements); the remaining 24 synthesized in laboratories
11. No element heavier than einsteinium (element 99) has ever been observed in macroscopic quantities in its pure form, nor has astatine (element 85); francium (element 87) has been only photographed in the form of light emitted from microscopic quantities (300,000 atoms)

Is this really what a reader needs? Just some points that occur to me, and a suggested sequence:

• This is the periodic table of elements yet there is no explanation of what an element is or why they are tabularised. Maybe define atoms as the building blocks of normal matter and that the table has evolved throughout history and is still being modified based on additional research as a way to summarise the properties.
• Stating that all elements are made of atoms, each consisting of a nucleus with protons and (usually) neutrons, surrounded by an electron cloud to provide charge balance
• Then address that 94 occur naturally and others have been synthesised
• Diagram of single PT cell, noting it provides name, symbol, atomic mass, atomic number = Z. Atomic mass the weighted average of naturally occurring isotopes
• Chemical properties largely arise from electrons and their configuration. Neutral atom, electrons = Z but can gain or lose to become ions
• Then offer PT, perhaps coloured just for shells / sub-shells to indicate that organisation occurs by preceding from previous element and looking to where the additional electron is placed – covering s-, p-, d-, and f- blocks and electronic configurations
• The present statement (6) is not correct. If O and Se are in the same column because they have 4 electrons in p subshell, why aren't they in same column as Be (as all have 2 electrons in outermost s subshell). Further, Cr is in group 6 suggesting a d⁴ configuration but we all know it is actually s¹d⁵, making positioning unclear under this statement. I know the answers, of course, but would a non-chemist understand from the statement made?
• Statement (7) – perhaps more useful to say that arrangement historically placed chemically similar elements together and that the arrangement by electronic configuration retains this as the similarity in valence shell configuration explains the similarity in chemical properties
• For heavier elements, and especially those in the f-block and to some extent the d-block, elements share similarities across periods. For this reason, the properties of elements can be predicted relatively easily in these parts of the PT if the properties of surrounding elements are known.
• This arrangement led to gaps for missing elements being identified and predictions made about their properties, which proved useful in the search for missing elements. All such gaps have now been filled. All elements up to einsteinium (element 99) have been observed in macroscopic quantities in pure form, with two exceptions - astatine (element 85) and francium (element 87), though the light emitted due to radioactive decay of a microscopic quantity of francium (300,000 atoms) has been photographed. No element beyond einsteinium has been observed in macroscopic form.
• Historically, alchemists sought elemental transmutation, changing one element into another – can only be achieved by changing the nucleus whereas chemical processes only rearrange electrons. However, by introducing radioactivity, we find that elements can spontaneously decay in which the nucleus is changed and element is transformed into another. The 94 naturally-occurring elements are divided into 83 primordial and 11 formed in the decay chains of some of the primordial elements
• Fusion, the combining of smaller atoms into larger ones, is possible and is responsible for the energy coming from the sun, and for the formation of all elements heavier than H. Fission, the splitting of heavier elements, can also be achieved for some elements and occurred for uranium and plutonium in Hiroshima and Nagasaki, respectively, at the end of WW2.
• Since WW2, scientists have investigated fusion processes to prepare new elements and in so doing have added 24 new elements to the PT, the latest being Nh, Mc, Ts, and Og that were confirmed in December 2015 and had their names / symbols assigned in November 2016. In each case, the new elements need evidence of their chemical properties to confirm that their anticipated position in the PT is correct. The mass shown is for the isotope of greatest stability, and given in parentheses to indicate that it is synthetic.
• Arrangements and categorisations have been debated over time. The historical division of elements into metals and non-metals based on chemical properties has been expanded to include metalloids with similarities to each group. Metals within the s-block are sometimes subdivided into alkali metals (group 1) and alkaline earth metals (group 2), while the d- and f-block elements are sometimes called transition metals and inner transition metals, respectively. The non-metals are also sub-categorised by groups into the pnictogens, chalcogens, halogens, and noble gases, though this leaves hydrogen and boron uncategorised. 18 column periodic tables have varying placements of the f-block, reflecting different views of the appropriate location for elements like lanthanum and lutetium. The PT below presents one widely-used layout, with colourings to signify categorisations within the PT as a means to concisely summarise the wealth of knowledge of the elements.

Going on from there, the PT article goes into categories, metals v non-metals, etc, which seems more like the content for an article on the history of the elements than for an article on the PT. After outlining what the PT is, doesn't next come history (how it came to be that way) with element properties history that led to changes in the PT appearing at the appropriate point in the development of the PT?

Do others see that we have a problem with the structure of the PT article itself, and that we should discuss this first? For example, I can see how the debate about colouring and blocks v. categories in the PT in the overview arises. For me, the table given is too complex, though it is suited for the lede image and the article, but in reorganising the overview in some way (perhaps as I suggest off the top of my head), there becomes a natural presentation with the categories complicated one at the end and a blocks option preceding it.

Thoughts \ Comments \ Suggestions \ Criticisms \ etc? EdChem (talk) 03:19, 17 October 2020 (UTC)[reply]

@EdChem: The periodic table is a map. In an encyclopaedia, world maps are usually coloured by region. Your thoughts are refreshing albeit they don't address the substance of many of our discussions re how to colour the map. That is to say, a reorganising of the article, in order to improve its clarity, can be done by anyone who gives some thought to its presentation flow, as you have carefully done.

The debates about colouring are not that important in one sense but on the other hand we like to get things "right", so to speak, and doubts have been raised among us, as to wether this is in fact the case.

From a survey of 62 more recent chemistry textbooks, just 15% confine their lede periodic tables to showing just the blocks. Hence the interest, as an encyclopaedia, in showing more than this. Encyclopedia Britannica starts with nine categories (their table and its colour scheme predates ours); the most popular periodic table in the web emulates the WP table. Sandbh (talk) 05:46, 17 October 2020 (UTC)[reply]

@Sandbh: Not quite, when it comes to https://ptable.com/ – you will notice that they colour the Zn group as transition metals even though we don't, that they talk about "lanthanoids" and "actinoids" following IUPAC even though we don't, that they show the table in 18-column form with a gap under yttrium even though we don't, and that when you click "Wide" or those placeholders the table expands to the Sc-Y-Lu form that we had in 2016 and that I still think we made a mistake in ever leaving. So even when the categories are this similar we can't expect agreement in other sources in quite the same way we can expect it (outside group 3) when it comes to the question "which element is in which block?". As for EB, they depart from ours even more strongly, by saying that group 3 are apparently not transition metals (although group 12 is – so much for IUPAC), accepting to use "halogens" as a category (with At and Ts coloured as halogens!), and refusing to use "metalloids" as a category. Categories are common indeed, but no one agrees on what they are and what elements go where. Why take a side, I ask? And are we even allowed to take a side by policy, I ask? ^_^ Double sharp (talk) 10:25, 17 October 2020 (UTC)[reply]

• @EdChem: Good and well-written point, EdChem. The short explanation (not justification) is: in my experience, the term "overview" was primarily used to give a visual overview of the graphic table itself full stop. As you write, that is not enough, especially since there is only this one section (no subsections) for what is the encyclopedic essence. I'll think of a new setup, using your numbered bulleted list. -DePiep (talk) 09:42, 17 October 2020 (UTC)[reply]

DS comment

@EdChem: I think you are almost totally right, both about what you suggest, and that the debates here are strictly speaking less important than how the lede and the overview are not doing their jobs. (In fact, there's at least one statement in the lede that is flat-out wrong. Six groups do not have accepted names, because IUPAC never said that the names applied to the whole group. Only for the alkaline earth metals did they name all the known elements in the group, and when element 120 is discovered that also goes out the window. ^_^)

In fact you remind me of my somewhat-naughty-for-WP user subpage when I tried to write as an example what I'd do if I had my pedagogical hat on rather than my encyclopaedic hat on:

User:Double sharp/Teaching periodicity

! That's certainly not OK for WP, but I now think it was worth doing as an exercise because even though the language changes a lot, it certainly sheds light on what the logical sequence is supposed to be.

I just have two little pet peeves with what you propose (albeit ones I can substantiate by reliable sources). Please don't take my expounding on this at length the wrong way; I love everything else about it. I just really really dislike especially the first one being gotten wrong when we actually have reliable sources getting it right. ^_^

Blocks, differentiating electrons, and electronic configurations.

This is something that I have had to complain about for ages, but no, the blocks do not come from the electron that differentiates an element from the previous one. I am sure of course that you know this, but I think we should not simplify this in such a way that the resulting statement is incorrect. Simplify yes, but we have to keep things correct; this is an encyclopaedia, we will get readers of every level, and we should probably not

lie to children

. To substantiate my case, I give some reliable sources below.

Yes, I know some books say that blocks come from differentiating electrons. But I think this is outweighed by the fact that reliable sources are in agreement that electrons are

literally indistinguishable. (Not to mention that I have never seen any reliable source that succeeded in defining what a differentiating electron is in such a way that the definition actually applies to cases like vanadium d³s² proceeding to chromium d⁵s¹, or lawrencium d⁰s²p¹ proceeding to rutherfordium d²s²p⁰, but that's a minor additional point.) Serious sources covering physics understand this. If you look at them, they may use the sloppy language, but they make it very clear and apologise that it is sloppy. Like Feynman's lectures on physics

:

“

For lithium, however, the situation becomes quite different. Where can we put the third electron? The third electron cannot go on top of the other two because both spin directions are occupied. (You remember that for an electron or any particle with spin 1/2 there are only two possible directions for the spin.) The third electron can’t go near the place occupied by the other two, so it must take up a special condition in a different kind of state farther away from the nucleus in part (c) of the figure. (We are speaking only in a rather rough way here, because in reality all three electrons are identical; since we cannot really distinguish which one is which, our picture is only an approximate one.)

”

So we cannot single out the 2s electron in a lithium atom and call it the differentiating electron because we cannot even distinguish which electron is the 2s electron. Yes, he talks roughly about the "third electron", but he says it's a rough way of talking, and explains that in reality we cannot distinguish which is the third electron.

I realise that using the sloppy language is very tempting. I am often tempted to use it too. Some people who know better do it, like

hypervalence

even if textbooks are being sluggish. And that would be because school-level textbooks have something else constraining them other than the facts: they need to simplify things to the reader who is only just encountering something new, and even if they want to do things right, they may have to conform to the official syllabus in their country.

Similarly, reliable sources understand that the situation with d and f block configurations is actually not too significant, whence I quote Feynman again:

“

In copper an electron is robbed from the 4s shell, finally completing the 3d shell. The energy of the 10, 1 combination is, however, so close to the 9, 2 configuration for copper that just the presence of another atom nearby can shift the balance. For this reason the two last electrons of copper are nearly equivalent, and copper can have a valence of either 1 or 2. (It sometimes acts as though its electrons were in the 9, 2 combination.) Similar things happen at other places and account for the fact that other metals, such as iron, combine chemically with either of two valences.

”

So it's not really that important that the configurations don't match. What we have, and every periodic table poster shows, are gas-phase configurations. This is a situation that is about as far from chemistry as you can get: a single atom with nothing else around. As Feynman quite clearly states, for many d elements the configuration can change depending on exactly what elements are around. This is also stated for f elements in Christian Jørgensen's lecture-paper The Loose Connection between Electron Configuration and the Chemical Behavior of the Heavy Elements (Transuranics). In the same author's review Influence of Rare Earths on Chemical Understanding and Classification he writes:

“	The two major reasons why this series intended for gaseous atoms strongly bewilders chemists is that undue emphasis is made on irrelevant irregularities (such as the chromium, rhodium, palladium . . . . , atoms) and that the lowest level of two different configurations, such as [Xe]4f96s2 and [Xe]4f85d16s2 are only separated by 285 cm−1 in the terbium atom, much less than 1% of the spreading of J-levels of each of the two configurations, and quite negligible for chemical purposes.	”
— Christian Jørgensen (1988), Influence of Rare Earths on Chemical Understanding and Classification

So, finding reliable sources to refute the simplification is not a trouble. The only trouble is that this is mostly explained in textbooks near the beginning of a chemistry course when d and f elements are not on anyone's mind, and so I suspect many textbooks will be sloppy about it just because the oversimplified version works perfectly for main group elements and the rest of the table can be swept under the rug. I know there is someone who explains it properly, and that's William B. Jensen:

“

Classification of an element in the periodic table is based on four steps: Assignment to a major block based on the kinds of available valence electrons (i.e., s, p, d, f, etc.). Assignment of the elements within each block to groups based on the total number of available valence electrons. Verification of the validity of the resulting block and group assignments through the establishment of consistent patterns in overall block, group, and period property trends. Verification that the elements are arranged in order of increasing atomic number as required by the periodic law.

”

Now, it's true that Jensen very strongly supports the Lu option, and that his criteria were stated in the context of that support. On the other hand, Lavelle in his reply (on the next page of that article) is a strong La supporter, and he also wrote "I agree with Jensen’s four points on classifying elements in the periodic table". Not to mention that the La vs Lu dispute is basically related to the foundations of what the PT is all about: outside textbooks, I suspect this is one of the few places where those things will be talked about rather than disregarded as obvious stuff known since school. Therefore I think we can use this one. It accords with the generally accepted science rather than being a pedagogical simplification; since we do not have our pedagogy hat on here, I feel we should focus on the former

So I'd replace some of your points in the middle (italics for what I've changed) with:

• Chemical properties largely arise from electrons and their configuration. Neutral atom, electrons = Z but can gain or lose to become ions
• Then offer PT, perhaps coloured just for shells / sub-shells to indicate that organisation occurs by looking at how many electrons are available for chemical reactions and which subshells they appear in; covering s-, p-, d-, and f- blocks.
• Statement (7) – perhaps more useful to say that arrangement historically placed elements with some chemical similarities together and that the arrangement by valence electrons and subshells retains this as the similarity in valence shell configuration explains the similarity in chemical properties.

This way, we avoid having to mention the electron configuration outright in the lede and need to explain exactly what needs to be fixed about that picture for the d and f elements; we cut straight to an easily explained version of the correct statement. A sentence on the problems with gas-phase configurations for d and f elements might be fine here only as a footnote. In the main body, of course, we can talk about this in a little bit more detail and promote it to the actual text.

And I say "elements with some chemical similarities" rather than "chemically similar elements" to avoid having wiseacres at the back of the classroom wonder how nitrogen and bismuth got into the same group even for Mendeleev. (I know, it's not a classroom, but probably the same personality type. ^_^) He was looking at the valence there, if I am not mistaken: for both elements maximum valence is +5. So that's a chemical property that matches even though many others don't, which is why I think my wording may be a bit better there. Again, it's just a fine line for me about being both simple and right.

Colourings to signify categories.

This thing at the very end segues into what I think is one of the two issues we are discussing. I don't even think we should colour to signify categories in the first place because nobody can agree on what categories to use and what their boundaries are. Yes, most textbooks show categories. But what categories? Anything we colour, like Se as a nonmetal rather than a metalloid (which one quarter of sources do!) or as a metal, picks a side. In the absence of a warning for just about any element near this borderline I feel that any colouring along a metallicity line gives undue weight to one side. Worse still, we outright put in places like {{infobox oxygen}} things like "Element category: Reactive nonmetal", as if the categories we had decided to use were the only ones that actually existed! No mention of chalcogens at all even though that is IUPAC-approved and "reactive nonmetals" is not! Meanwhile we cannot even get all the IUPAC-approved and common categories in there without overlaps (where did pnictogens and chalcogens go?)!

I think you are correct, EdChem, to prioritise pnictogens and chalcogens in the lede over those metallicity p block categories, because the former are actually IUPAC-approved and the latter are not. But I think that for the above reasons, what is best is to display nothing but blocks as a general thing for colouring our general PT images. Outside the group 3 issue (which is something else in itself), which elements belong in which block is at least something that is 100% agreed on by everybody. Many textbooks colour more than that indeed; but I find it likely that most of those textbooks also know what a block is and talk about it when explaining the structure of the periodic table.

Once that one almost-universally agreed thing is done, then we can talk about categories. And by talking about them, we eliminate the sticking point that many of them overlap and that chemists don't agree on the scope of each category. Sandbh has already given two sources that disagree with the WP colour scheme. The fact that the literature is split 50-50 on whether the Zn group should be considered transition elements or not should already caution us about any colour scheme in the first place! Those are hard to reflect in a picture where we have to colour each category clearly. But if we just want to describe where each category lives in the table with text, then everything is 100% fine!

So we can talk about the chalcogens category (O, S, Se, Te, Po), without in any way jeopardising other categories like metalloids that commonly includes Te and sometimes Po, or post-transition metals or the myriad of other similar categories that quite often include Po. And we can talk about the transition metals as a category while making it clear that there's disagreement in the literature about group 12, without having to pick a side when colouring. I feel that would reflect the large spread of what the sources do far better than any colouring choice would do. So I would prefer to replace your last sentence with: "The PT below presents one widely-used layout, with colourings to signify blocks; many tables also colour in specific categories, many of which are described below."

Looking forward to your comments. And sorry for spending so long on what amount to such minor proposed changes from what you've very kindly suggested when I love almost everything about what you've written; it's just that once you know that the first thing is not quite right, you get slightly annoyed whenever you see it wrong. ^_^ Double sharp (talk) 10:16, 17 October 2020 (UTC)[reply]

I am happy to find DS here saying what I wrote below (in an ec): for the first description of the PT, we could remove the categorisation and catogory colors. And to point to another suggestion DS made (in their userpage); from memory: "when discussing elements, we should talk about their concept as specimen [~gas-phase then? DP], and forget about their appearance in RL chemistry" (IIRC). In element pages, that would mean we should move to bottom of page: diatomic substances (O₂), allotropes, std atomic mass even. Could also conceptually simplify the PT article. -DePiep (talk) 11:25, 17 October 2020 (UTC)[reply]

@DePiep: I don't remember exactly what I said, but from what you say it might have been the distinction between the chemical element as in atoms and as in simple substances. So, oxygen as in "the type of atom with eight protons in its nucleus", rather than as dioxygen the gas or ozone the gas, because oxygen the element is just as present in MgO or CO₂ as it is in O₂ or O₃. Sure, that's an important concept too: Jensen talks about it here. The only trouble is that this distinction is, AFAIK, not clear enough often in English-language sources. So while I would dearly like to get rid of the conflation of the two notions, as French Wikipedia could do, I am not sure if we can. Maybe we have to do what Polish Wikipedia does and admit that in our language "chemical element" has two meanings. Remember, on my userpages I sometimes say things that are not standard yet, just significant minority viewpoints that I happen to agree with, and I try to keep that separate from the articles. ^_^ Double sharp (talk) 12:52, 17 October 2020 (UTC)[reply]

P.S. Glad to hear you're in agreement too about categorisation and category colours. ^_^ But I go a bit further and advocate removing them altogether from the infoboxes and PT templates. There are simply too many categories in the literature that overlap and have fuzzy boundaries for me to think that trying to interpret this as "there are a finite set of categories we use, some elements are disputed" is acceptable. To my taste anyway. It is a failing at following reliable sources, IMHO, that we mark out oxygen as just a reactive nonmetal but not also as a chalcogen. The latter category is IUPAC-approved when the former is not; it just fits badly in a scheme that tries to cover every element once and once only. I once again plead that we follow reliable sources, and noting that categories may differ very widely whereas blocks don't outside the group 3 dispute, suggest that the best way to do that is to not take sides on categories by not colouring them everywhere. Only describing them. I strongly support saying in the articles things like "Selenium is a chalcogen, and has been variously classified as a nonmetal, metal, or metalloid (most often the former)" (for the selenium article); I do not support trying to reduce this situation to colouring it only as one category everywhere. Double sharp (talk) 13:06, 17 October 2020 (UTC)[reply]

Remove cat+colors altogether (except for dedicated articles + their PT graphs) better be discussed separately, to keep thread on topic. But indeed removing them when describing the PT in its main article is helpful (because: another non-essential detail; and a very attentionseeking distraction at that). Now let's look further on what more should be in/out of the Overview. -DePiep (talk) 13:26, 17 October 2020 (UTC)[reply]

@DePiep: OK, new top-level section coming at some point to keep that issue separate. I won't discuss it here anymore. ^_^ Double sharp (talk) 13:33, 17 October 2020 (UTC)[reply]

DePiep comment

Following up EdChems post.

• New Overview setup thoughts

As a first suggestion, we could overhaul the "Overview" section & intention like this.

In general: it should describe the PT's essence (structure, relations, resulting appearance). This also implies:

0. Leave out details that are irrelevant to the goal (advantage: makes it easier to build the descrition without sidetracking). So for the overview, do not mention: history (Mendeleev, intermediate PT forms), isotopes, discovery of elements (new, predicted, added noble gasses), open issues (He placement, group 3), difference between concept (specimen) of an element and its RL appearance: use the concept only (no allotropes, difference natural/synthetic, atomic mass vs. Z -- though A=Z+N might be needed), alternative structures (Janet's left step), alternative graphic layouts (18/32 column), categories and other secondary trends/patterns(!). However, is an extra, late subthread we can introduce a few of those, as being related to the PT.

Section: Overview (==-level). Subsections:

1. Section: Element. Note chemical and physical difference (we need later on). Mention valence (0, I-VIII). Add single cell graphic example+explanation.

2. Section: Build the PT yourself (as is has been build before). Step 1: Order all elements 1-118 in a single line, one cell each, by increasing Z. (This order shall not change!). Step 2: Add a linebreak and blank cells such that: in the second row, elements with similar chemical behaviour (same valence, by RxOy valence) are in the same column. Repeat this (you'll need six linebreaks, creating seven rows). +example maybe.

3. Section: PT graph (simplified into essentials only, add group valence, rm catcolors?)

4. Section: explain hiccups as simple as possible: A/B valence columns, no-valence for f-block, blank cells in upper part & blocks. Or write: "described and explained in [wl]".

5. Section: Physical background. Shell filling & valence, blocks, A=Z+N (but not isotopes).

6. Section: Other patterns and properties (could be new ==-level section, still overview only), e.g.: categories (metal-nonmetal, maybe subcategories?), isotopes, RL appearance as A_{r, std} and allotropes, m.p. b.p., discovery of elements.

7. Section: Related topics. Introducing like isotopes, graphical variants, structural variants, some historical problems now solved.

Below, existing sections on PT aspects can stay (though checked for consistency, and reordered by being essential and non-essential aspects).

This tries to make a buildup line for a complete description. The tough parts will be to leave out details as much as possible, then write the remaining stuff to the point. From here on, I'll leave it to you to write it :-) -DePiep (talk) 11:02, 17 October 2020 (UTC)[reply]

@DePiep: I think you have a point: the overview should, to my taste, simply be about the theoretical justification for the PT where the PT comes from, how to read it, and the patterns that come from it. At the very least, I think the current organisation is simply not good: blocks and periods should come before categories, and Klechkovsky's / Madelung's rule should appear far earlier than it actually does. I am not so sure about some of the details you mention, but I think we are in agreement on the basic idea. I can try to write it, but I'm busy and it may take a while. ;) Double sharp (talk) 12:57, 17 October 2020 (UTC)[reply]

@Double sharp: Well, describe by theoretical justification is quite different from describe by the (historical, Mendeleevian) buildup. Looks like it is the approach from the opposite direction (explaining vs. discovering). If by theoretical justification you mean "Classification of an element in the periodic table is based on four steps" (per Jensen; you wrote above), with me the question raises: what 'classification' is that? Does it inevitable lead to the column/row structure, so essential to the PT? As opposed to, say, enwiki-like categories, or electron filling issues solved -- IMO not essential in this. A warning is that ascending Z has to be "verified" in step 4. As far as I, interested layman, understand it now, the theor'al.justif'ion, it would add a strong physical base (e.g., shell filling), but I do not recognise yet how it would describe periodicity encyclopedically. Alas, we'll see what others think. -DePiep (talk) 13:19, 17 October 2020 (UTC)[reply]

@DePiep: Yes, it's about the column/row structure. Jensen uses this to put elements in blocks, then in groups within blocks, and then verifies that the resulting placement may make sense. His approach is not everybody's, but the general idea that there's something about electronic structure that explains the PT structure is present across sources. The point of the periodic law is that the configurations of the atoms and hence the properties of the elements depend periodically on atomic number. So I'd describe periodicity as such (statements of the periodic law can be found in the literature) and then describe the subshell filling that justifies it. And I think this is already done in EdChem's proposal. Of course, historically that is not at all where it came from, but I think that is something that should be covered under "History".

As for the words "theoretical justification": yeah, in the literature this is apparently controversial, regarding the actual status of Klechkovsky's rule for one. I dislike that situation, but it is what it is and we have to reflect it. So, OK, I should have said basically where the PT comes from. So I've struck my words out and corrected it. ^_^ But let's work on the details later and focus on EdChem's proposal first. Double sharp (talk) 14:34, 17 October 2020 (UTC)[reply]

P.S. I guess perhaps it might be better now that I briefly think about it again to first show the table, mention that periods are rows and groups are columns and the blocks are those rectangular areas, before stating where all of this comes from to explain what they mean. Double sharp (talk) 15:38, 17 October 2020 (UTC)[reply]

YBG comments

@EdChem: Thank you for giving a fresh review to our PT article; I agree largely with what you say, but I have a few questions.

Where to from here? Here are some ideas, in no particular order.

1. Re #EdChem's PT article proposal @DePiep, Double sharp, and Sandbh: You have each expressed some agreement and some disagreements with EdChem's suggestions. Is there any subset of the suggestions that is generally agreed upon that could be implemented apart from the remainder? If so, I think a good first step would be to implement agreed upon aspects before deciding the areas where we have disagreement. But I don't know if those areas are in fact separable. Does anyone think this possible?
2. Re DePiep's #Build the PT yourself idea. This sounds like an excellent idea for an animated graphic. I'm not sure if this is something for WP or an off-wiki project.
3. Re Double sharp's #Colourings to signify categories, specifically Anything we colour ... picks a side. I have been struggling with how to do a better job of representing all names for sets of chemical elements and not just the "winners" from our past and future mega threads. I have come up with two ideas which I think can be and benefit our encyclopedia and could be implemented independently of any other efforts, and even more importantly, could remain in place even if we make substantial changes to our category coloring system. Here are my ideas:
   • (3a) For each named set of chemical elements, develop a page modeled after lists of metalloids. This represents a substantial amount of work, but I think it would have great benefit. If Sandbh were willing to take this on, we could depend on his research skills to make these lists complete and reflective of the literature.
   • (3b) Change our {{infobox element}} by replacing "Element category" with "Element categories" and including a list of all names for sets of chemical elements that generally include the given element, possibly distinguishing the sets an element is almost always included in from the sets that less frequently include it, but probably excluding sets that very rarely include the element. This also represents a substantial amount of work, and should eventually be coordinated with the previous work, but the first draft need not wait on that result. If DePiep were willing to take this on, we could depend on his template-building skill to fully integrate this information into our template system, maybe by adding {{Infobox element/symbol-to-category-list}}, something along the lines of {{Infobox element/symbol-to-valence-group}}

The common thread in these items is my desire to get the most reader-bang-for-the-editor-buck by finding changes that improve our corner of WP without waiting for some hard-to-reach consensus. By all means, we should tackle the more difficult issues, but at the same time we should intentionally find non-controversial efforts that provide us with significant improvement. This will maximize the benefit the readers receive from the effort we editors put in. YBG (talk) 18:13, 17 October 2020 (UTC)[reply]

@YBG: my replies in ~short:

re 1. Looks like both EdChem, DS and me agree that the Periodic table#Overview section needs a complete redesign. Note that this section is the only one in article that handles the whole if it; other sections are just aspects. (Just showing a PT graph with some clarifications is not enough). This is the general agreement. Listing details, subtopics and incidental miswritings as issues does not help, once appreciated that we do need a redesign to rewrite this encyclopedically. For this, I'd definitely prefer to agree on a general line of approach (say section titles) to describe the PT.

re 2. When I wrote "Build a PT yourself", that's not a final text proposal TBH. But it does say the good part: being good science, the Reader can reproduce the original, Mendelevian 'experiment'. (Personally, when introducing the PT to people I learned that, after defining 'element' first, the Z-order is not to be skipped (having to smuggle with weight vs. Z). Only then the rhythm eh periodicity can be introduced (my 'line break' thing is useful in such a talk). So I build my proposal along this 'Mendeleevian' line.

OTOH, Double sharp gives an other approach: describe periodicity from the physical atom model. Our first task is to find a good overall line for the Overview. To keep in mind: needs an encyclopedic result for sure.

re 3a. We could treat each "category" (i.e., any set of elements, not just our enwiki nine) equally, at least create a good set of articles & overvierw lists. However, could be that categories are not part of the future redesigned PT#Overview section at all ;-) -DePiep (talk) 18:48, 17 October 2020 (UTC)[reply]

re 3b. Of course we can develop that categories-list-per-element. Let's get the articles right first ;-) -DePiep (talk) 18:48, 17 October 2020 (UTC)[reply]