Group 4 element

This is a good article. Click here for more information.
Source: Wikipedia, the free encyclopedia.
Group 4 in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
group 3 ←    → group 5
IUPAC group number 4
Name by element titanium group
CAS group number
(US, pattern A-B-A)
 IVB
old IUPAC number
(Europe, pattern A-B)
 IVA
↓ Period
4
Image: Titanium crystal bar
Titanium (Ti)
22 Transition metal
5
Image: Zirconium crystal bar
Zirconium (Zr)
40 Transition metal
6
Image: Hafnium crystal bar
Hafnium (Hf)
72 Transition metal
7 Rutherfordium (Rf)
104 Transition metal
Legend
primordial element
Black atomic number: solid

Group 4 is the second group of transition metals in the periodic table. It contains the four elements titanium (Ti), zirconium (Zr), hafnium (Hf), and rutherfordium (Rf). The group is also called the titanium group or titanium family after its lightest member.

As is typical for early transition metals, zirconium and hafnium have only the group oxidation state of +4 as a major one, and are quite electropositive and have a less rich coordination chemistry. Due to the effects of the lanthanide contraction, they are very similar in properties. Titanium is somewhat distinct due to its smaller size: it has a well-defined +3 state as well (although +4 is more stable).

All the group 4 elements are hard,

radioactive
: it does not occur naturally and must be produced by artificial synthesis, but its observed and theoretically predicted properties are consistent with it being a heavier homologue of hafnium. None of them have any biological role.

History

Jöns Jakob Berzelius isolated an impure form of zirconium, obtained by heating a mixture of potassium and potassium zirconium fluoride in an iron tube.[1]

Cornish mineralogist

Titans of Greek mythology.[5] Berzelius was also the first to prepare titanium metal (albeit impurely), doing so in 1825.[6]

The

rare earth elements in 1907 and published his results on celtium in 1911.[9] Neither the spectra nor the chemical behavior he claimed matched with the element found later, and therefore his claim was turned down after a long-standing controversy.[10]

By early 1923, several physicists and chemists such as

Georg von Hevesy were motivated to search for the new element in zirconium ores.[15] Hafnium was discovered by the two in 1923 in Copenhagen, Denmark.[16][17] The place where the discovery took place led to the element being named for the Latin name for "Copenhagen", Hafnia, the home town of Niels Bohr.[18]

Hafnium was separated from zirconium through repeated recrystallization of the double ammonium or potassium fluorides by Valdemar Thal Jantzen and von Hevesy.[19] Anton Eduard van Arkel and Jan Hendrik de Boer were the first to prepare metallic hafnium by passing hafnium tetraiodide vapor over a heated tungsten filament in 1924.[20][21] The long delay between the discovery of the lightest two group 4 elements and that of hafnium was partly due to the rarity of hafnium, and partly due to the extreme similarity of zirconium and hafnium, so that all previous samples of zirconium had in reality been contaminated with hafnium without anyone knowing.[22]

The last element of the group,

IUPAP, the Transfermium Working Group, decided that credit for the discovery should be shared. After various compromises were attempted, in 1997 IUPAC officially named the element rutherfordium following the American proposal.[26]

Characteristics

Chemical

Electron configurations of the group 4 elements
Z Element Electron configuration
22 Ti, titanium 2, 8, 10,  2 [Ar]      3d2 4s2
40 Zr, zirconium 2, 8, 18, 10,  2 [Kr]      4d2 5s2
72 Hf, hafnium 2, 8, 18, 32, 10,  2 [Xe] 4f14 5d2 6s2
104 Rf, rutherfordium 2, 8, 18, 32, 32, 10, 2 [Rn] 5f14 6d2 7s2

Like other groups, the members of this family show patterns in their electron configurations, especially the outermost shells, resulting in trends in chemical behavior. Most of the chemistry has been observed only for the first three members of the group; chemical properties of rutherfordium are not well-characterized, but what is known and predicted matches its position as a heavier homolog of hafnium.[27]

Titanium, zirconium, and hafnium are reactive metals, but this is masked in the bulk form because they form a dense oxide layer that sticks to the metal and reforms even if removed. As such, the bulk metals are very resistant to chemical attack; most aqueous acids have no effect unless heated, and aqueous alkalis have no effect even when hot. Oxidizing acids such as nitric acids indeed tend to reduce reactivity as they induce the formation of this oxide layer. The exception is hydrofluoric acid, as it forms soluble fluoro complexes of the metals. When finely divided, their reactivity shows as they become pyrophoric, directly reacting with oxygen and hydrogen, and even nitrogen in the case of titanium. All three are fairly electropositive, although less so than their predecessors in group 3.[28] The oxides TiO2, ZrO2 and HfO2 are white solids with high melting points and unreactive against most acids.[29]

The chemistry of group 4 elements is dominated by the group oxidation state. Zirconium and hafnium are in particular extremely similar, with the most salient differences being physical rather than chemical (melting and boiling points of compounds and their solubility in solvents).[29] This is an effect of the lanthanide contraction: the expected increase of atomic radius from the 4d to the 5d elements is wiped out by the insertion of the 4f elements before. Titanium, being smaller, is distinct from these two: its oxide is less basic than those of zirconium and hafnium, and its aqueous chemistry is more hydrolyzed.[28] Rutherfordium should have a still more basic oxide than zirconium and hafnium.[30]

The chemistry of all three is dominated by the +4 oxidation state, though this is too high to be well-described as totally ionic. Low oxidation states are not well-represented for zirconium and hafnium[28] (and should be even less well-represented for rutherfordium);[30] the +3 oxidation state of zirconium and hafnium reduces water. For titanium, this oxidation state is merely easily oxidised, forming a violet Ti3+ aqua cation in solution. The elements have a significant coordination chemistry: zirconium and hafnium are large enough to readily support the coordination number of 8. All three metals however form weak sigma bonds to carbon and because they have few d electrons, pi backbonding is not very effective either.[28]

Physical

The trends in group 4 follow those of the other early d-block groups and reflect the addition of a filled f-shell into the core in passing from the fifth to the sixth period. All the stable members of the group are silvery

body-centered cubic structure. While they are better conductors of heat and electricity than their group 3 predecessors, they are still poor compared to most metals. This, along with the higher melting and boiling points, and enthalpies of fusion, vaporization, and atomization, reflects the extra d electron available for metallic bonding.[32]

The table below is a summary of the key physical properties of the group 4 elements. The four question-marked values are extrapolated.[34]

Properties of the group 4 elements
Name Ti, titanium Zr, zirconium Hf, hafnium Rf, rutherfordium
Melting point 1941 K (1668 °C) 2130 K (1857 °C) 2506 K (2233 °C) 2400 K (2100 °C)?
Boiling point 3560 K (3287 °C) 4682 K (4409 °C) 4876 K (4603 °C) 5800 K (5500 °C)?
Density 4.507 g·cm−3 6.511 g·cm−3 13.31 g·cm−3 17 g·cm−3?
Appearance silver metallic silver white silver gray ?
Atomic radius 140 pm 155 pm 155 pm 150 pm?

Titanium

This section is transcluded from Titanium. (edit | history)

As a

thermal conductivity compared to other metals.[36] Titanium is superconducting when cooled below its critical temperature of 0.49 K.[39][40]

Zirconium

This section is transcluded from Zirconium. (edit | history)

Zirconium is a

brittle at lesser purities.[2] In powder form, zirconium is highly flammable, but the solid form is much less prone to ignition. Zirconium is highly resistant to corrosion by alkalis, acids, salt water and other agents.[1] However, it will dissolve in hydrochloric and sulfuric acid, especially when fluorine is present.[41] Alloys with zinc are magnetic at less than 35 K.[1]

Hafnium

This section is transcluded from Hafnium. (edit | history)

Hafnium is a shiny, silvery, ductile metal that is corrosion-resistant and chemically similar to zirconium[42] in that they have the same number of valence electrons and are in the same group. Also, their relativistic effects are similar: The expected expansion of atomic radii from period 5 to 6 is almost exactly canceled out by the lanthanide contraction. Hafnium changes from its alpha form, a hexagonal close-packed lattice, to its beta form, a body-centered cubic lattice, at 2388 K.[43] The physical properties of hafnium metal samples are markedly affected by zirconium impurities, especially the nuclear properties, as these two elements are among the most difficult to separate because of their chemical similarity.[42]

Rutherfordium

This section is transcluded from Rutherfordium. (edit | history)

Rutherfordium is expected to be a solid under normal conditions and have a

body-centered cubic crystal structure; hafnium transforms to this structure at 71±1 GPa, but has an intermediate ω structure that it transforms to at 38±8 GPa that should be lacking for rutherfordium.[46]

Production

The production of the metals itself is difficult due to their reactivity. The formation of oxides, nitrides, and carbides must be avoided to yield workable metals; this is normally achieved by the Kroll process. The oxides (MO2) are reacted with coal and chlorine to form the chlorides (MCl4). The chlorides of the metals are then reacted with magnesium, yielding magnesium chloride and the metals.

Further purification is done by a chemical transport reaction developed by Anton Eduard van Arkel and Jan Hendrik de Boer. In a closed vessel, the metal reacts with iodine at temperatures above 500 °C forming metal(IV) iodide; at a tungsten filament of nearly 2000 °C the reverse reaction happens and the iodine and metal are set free. The metal forms a solid coating on the tungsten filament and the iodine can react with additional metal resulting in a steady turnover.[29][21]

M + 2 I2 (low temp.) → MI4
MI4 (high temp.) → M + 2 I2

Occurrence

Heavy minerals (dark) in a quartz beach sand (Chennai, India).

The abundance of the group 4 metals decreases with increase of atomic mass. Titanium is the seventh most abundant metal in Earth's crust and has an abundance of 6320 ppm, while zirconium has an abundance of 162 ppm and hafnium has only an abundance of 3 ppm.[47]

All three stable elements occur in

specific gravity of the mineral grains of erosion material from mafic and ultramafic rock. The titanium minerals are mostly anatase and rutile, and zirconium occurs in the mineral zircon. Because of the chemical similarity, up to 5% of the zirconium in zircon is replaced by hafnium. The largest producers of the group 4 elements are Australia, South Africa and Canada.[48][49][50][51][52]

Applications

Titanium metal and its alloys have a wide range of applications, where the corrosion resistance, the heat stability and the low density (light weight) are of benefit. The foremost use of corrosion-resistant hafnium and zirconium has been in nuclear reactors. Zirconium has a very low and hafnium has a high

fuel rods in nuclear reactors,[42] while hafnium is used in control rods for nuclear reactors, because each hafnium atom can absorb multiple neutrons.[53][54]

Smaller amounts of hafnium[55] and zirconium are used in super alloys to improve the properties of those alloys.[56]

Biological occurrences

The group 4 elements are hard refractory metals with low aqueous solubility and low availability to the biosphere.

Titanium is not required for any role in any organism's biology. However, many studies suggest that titanium could be biologically active. Most titanium on Earth is stored within insoluble minerals, so it is unlikely to be a part of any biological system in spite of being potentially biologically active.[57]

Zirconium plays no known role in any biological system, and has low toxicity.[58]

Hafnium plays no known role in any biological system, and has low toxicity.[59]

Rutherfordium's radioactivity of just a couple of hours would make it toxic to living cells. However, it is a synthetic element, so it does not occur in nature or the human body.

Precautions

Titanium is non-toxic even in large doses and does not play any natural role inside the

silica. One study indicates a possible connection between titanium and yellow nail syndrome.[61]

Zirconium powder can cause irritation, but only contact with the eyes requires medical attention.[62] OSHA recommendations for zirconium are 5 mg/m3 time weighted average limit and a 10 mg/m3 short-term exposure limit.[63]

Only limited data exists on the toxicology of hafnium.

pyrophoric—fine particles can spontaneously combust when exposed to air. Compounds that contain this metal are rarely encountered by most people. The pure metal is not considered toxic, but hafnium compounds should be handled as if they were toxic because the ionic forms of metals are normally at greatest risk for toxicity, and limited animal testing has been done for hafnium compounds.[64]

References

  1. ^
    ISBN 978-0-8493-0488-0
    .
  2. ^ a b Emsley 2001, pp. 506–510
  3. ^ a b Emsley 2001, p. 452
  4. ^ Barksdale 1968, p. 732
  5. doi:10.1021/ed009p1231
    .
  6. ^ Greenwood and Earnshaw, p. 954
  7. S2CID 144765815
    .
  8. doi:10.1080/00033796700203306
    .
  9. ^ Urbain, M. G. (1911). "Sur un nouvel élément qui accompagne le lutécium et le scandium dans les terres de la gadolinite: le celtium (On a new element that accompanies lutetium and scandium in gadolinite: celtium)". Comptes Rendus (in French): 141. Retrieved 2008-09-10.
  10. doi:10.1111/j.1600-0498.1982.tb00667.x
    .
  11. ISBN 978-1-4365-0368-6
    .
  12. doi:10.1021/ja01440a023
    .
  13. ^ Paneth, F. A. (1922). "Das periodische System (The periodic system)". Ergebnisse der Exakten Naturwissenschaften 1 (in German). p. 362.
  14. doi:10.1021/ed059p242. Archived from the original
    (PDF) on 2020-03-15. Retrieved 2021-02-03.
  15. ^ Urbain, M. G. (1922). "Sur les séries L du lutécium et de l'ytterbium et sur l'identification d'un celtium avec l'élément de nombre atomique 72" [The L series from lutetium to ytterbium and the identification of element 72 celtium]. Comptes Rendus (in French). 174: 1347. Retrieved 2008-10-30.
  16. doi:10.1038/111079a0
    .
  17. doi:10.1021/cr60005a001
    .
  18. doi:10.1080/00033799400200161
    .
  19. doi:10.1002/zaac.19241410117
    .
  20. doi:10.1002/zaac.19241410118
    .
  21. ^
    doi:10.1002/zaac.19251480133
    .
  22. LCCN 68-29938
    .
  23. S2CID 195819585
    .
  24. doi:10.1103/PhysRevLett.22.1317
    .
  25. ^ "Rutherfordium". Rsc.org. Retrieved 2010-09-04.
  26. doi:10.1351/pac199769122471
    .
  27. S2CID 96299943. Archived from the original
    (PDF) on 2008-05-28.
  28. ^ a b c d Greenwood and Earnshaw, pp. 958–61
  29. ^
    ISBN 3-11-007511-3
    .
  30. ^ a b Periodic table poster by A. V. Kulsha and T. A. Kolevich
  31. ^ Greenwood and Earnshaw, pp. 956–8
  32. ^ a b Greenwood and Earnshaw, pp. 946–8
  33. ^
    doi:10.1103/PhysRevB.84.113104
    .
  34. ^
    ISBN 1-4020-3555-1
    .
  35. ISBN 978-0-7876-5015-5
    .
  36. ^ a b "Titanium". Encyclopædia Britannica. 2006. Retrieved 19 January 2022.
  37. ISBN 978-0-19-508083-4
    .
  38. ^ "Is Titanium A Refractory Metal". Special Metal Fabrication.
  39. doi:10.1103/PhysRev.92.243
    .
  40. S2CID 54891002
    .
  41. ISBN 978-0-471-61525-5
    .
  42. ^
    ISBN 978-0-8031-0505-8
    .
  43. doi:10.1063/1.4880657
    .
  44. doi:10.1103/PhysRevB.83.172101
    .
  45. ^ Kratz; Lieser (2013). Nuclear and Radiochemistry: Fundamentals and Applications (3rd ed.). p. 631.
  46. arXiv:1106.3146 [cond-mat.mtrl-sci
    ].
  47. ^ "Abundance in Earth's Crust". WebElements.com. Archived from the original on 2008-05-23. Retrieved 2007-04-14.
  48. ^ "Dubbo Zirconia Project Fact Sheet" (PDF). Alkane Resources Limited. June 2007. Archived from the original (PDF) on 2008-02-28. Retrieved 2008-09-10.
  49. ^ "Zirconium and Hafnium" (PDF). Mineral Commodity Summaries. US Geological Survey: 192–193. January 2008. Retrieved 2008-02-24.
  50. ^ Callaghan, R. (2008-02-21). "Zirconium and Hafnium Statistics and Information". US Geological Survey. Retrieved 2008-02-24.
  51. ^ "Minerals Yearbook Commodity Summaries 2009: Titanium" (PDF). US Geological Survey. May 2009. Retrieved 2008-02-24.
  52. ^ Gambogi, Joseph (January 2009). "Titanium and Titanium dioxide Statistics and Information" (PDF). US Geological Survey. Retrieved 2008-02-24.
  53. ^ Hedrick, James B. "Hafnium" (PDF). United States Geological Survey. Retrieved 2008-09-10.
  54. doi:10.1021/ie50614a019
    .
  55. ^ Hebda, John (2001). "Niobium alloys and high Temperature Applications" (PDF). CBMM. Archived from the original (PDF) on 2008-12-17. Retrieved 2008-09-04.
  56. ISBN 978-0-87170-749-9
    .
  57. ^ "Contemplating a role for titanium in organisms". academic.oup.com. Retrieved 2023-09-23.
  58. ^ "Zirconium - Element information, properties and uses | Periodic Table". www.rsc.org. Retrieved 2023-09-23.
  59. ^ "Hafnium - Element information, properties and uses | Periodic Table". www.rsc.org. Retrieved 2023-09-23.
  60. ^
    ISBN 978-0-19-850341-5.[verification needed
    ]
  61. PMID 20809268
    .
  62. ^ "Zirconium". International Chemical Safety Card Database. International Labour Organization. October 2004. Retrieved 2008-03-30.
  63. ^ "Zirconium Compounds". National Institute for Occupational Health and Safety. 2007-12-17. Retrieved 2008-02-17.
  64. ^ a b "Occupational Safety & Health Administration: Hafnium". U.S. Department of Labor. Archived from the original on 2008-03-13. Retrieved 2008-09-10.

Bibliography

Retrieved from "https://en.wikipedia.org/w/index.php?title=Group_4_element&oldid=1215051240"