Chalcogen

Source: Wikipedia, the free encyclopedia.

Chalcogens
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
pnictogens ←    → halogens
IUPAC group number 16
Name by element oxygen group
Trivial name chalcogens
CAS group number
(US, pattern A-B-A)
 VIA
old IUPAC number
(Europe, pattern A-B)
 VIB
↓ Period
2
Other nonmetal
3
Other nonmetal
4
Other nonmetal
5
Image: Tellurium in metallic form
Tellurium (Te)
52 Metalloid
6
Other metal
7 Livermorium (Lv)
116 Other metal

Legend

primordial element
naturally occurring by radioactive decay
synthetic element
Atomic number color:
red=gas, black=solid

The chalcogens (ore forming) (/ˈkælkədʒənz/ KAL-kə-jənz) are the chemical elements in group 16 of the periodic table.[1] This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive elements polonium (Po) and livermorium (Lv).[2] Often, oxygen is treated separately from the other chalcogens, sometimes even excluded from the scope of the term "chalcogen" altogether, due to its very different chemical behavior from sulfur, selenium, tellurium, and polonium. 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 and coin),[3] and the Latinized Greek word genēs, meaning born or produced.[4][5]

Sulfur has been known since antiquity, and oxygen was recognized as an element in the 18th century. Selenium, tellurium and polonium were discovered in the 19th century, and livermorium in 2000. All of the chalcogens have six valence electrons, leaving them two electrons short of a full outer shell. Their most common oxidation states are −2, +2, +4, and +6. They have relatively low atomic radii, especially the lighter ones.[6]

All of the naturally occurring chalcogens have some role in biological functions, either as a nutrient or a toxin. Selenium is an important nutrient (among others as a building block of selenocysteine) but is also commonly toxic.[7] Tellurium often has unpleasant effects (although some organisms can use it), and polonium (especially the isotope polonium-210) is always harmful as a result of its radioactivity.

Sulfur has more than 20

allotropes, oxygen has nine, selenium has at least eight, polonium has two, and only one crystal structure of tellurium has so far been discovered. There are numerous organic chalcogen compounds. Not counting oxygen, organic sulfur compounds are generally the most common, followed by organic selenium compounds and organic tellurium compounds. This trend also occurs with chalcogen pnictides and compounds containing chalcogens and carbon group
elements.

Oxygen is generally obtained by separation of air into nitrogen and oxygen.[8] Sulfur is extracted from oil and natural gas. Selenium and tellurium are produced as byproducts of copper refining. Polonium is most available in naturally occurring actinide-containing materials. Livermorium has been synthesized in particle accelerators. The primary use of elemental oxygen is in steelmaking.[citation needed] Sulfur is mostly converted into sulfuric acid, which is heavily used in the chemical industry.[7] Selenium's most common application is glassmaking. Tellurium compounds are mostly used in optical disks, electronic devices, and solar cells. Some of polonium's applications are due to its radioactivity.[2]

Properties

Atomic and physical

Chalcogens show similar patterns in electron configuration, especially in the outermost shells, where they all have the same number of valence electrons, resulting in similar trends in chemical behavior:

Z Element No. of electrons/shell
8 Oxygen 2, 6
16 Sulfur 2, 8, 6
34 Selenium 2, 8, 18, 6
52 Tellurium 2, 8, 18, 18, 6
84 Polonium 2, 8, 18, 32, 18, 6
116 Livermorium 2, 8, 18, 32, 32, 18, 6 (predicted)[9]
Element Melting point
(°C)[6] 		Boiling point
(°C)[6] 		Density at STP
(g/cm3)[6]
Oxygen −219 −183 0.00143
Sulfur 120 445 2.07
Selenium 221 685 4.3
Tellurium 450 988 6.24
Polonium 254 962 9.2
Livermorium 220 (predicted) 800 (predicted) 14 (predicted)[9]

All chalcogens have six

conduct heat well.[6] Electronegativity decreases towards the chalcogens with higher atomic numbers. Density, melting and boiling points, and atomic and ionic radii[11] tend to increase towards the chalcogens with higher atomic numbers.[6]

Isotopes

Out of the six known chalcogens, one (oxygen) has an atomic number equal to a nuclear

observationally stable or nearly stable isotopes, 26 radioactive isotopes, and 9 isomers. Tellurium has eight stable or nearly stable isotopes, 31 unstable ones, and 17 isomers. Polonium has 42 isotopes, none of which are stable.[13] It has an additional 28 isomers.[2] In addition to the stable isotopes, some radioactive chalcogen isotopes occur in nature, either because they are decay products, such as 210Po, because they are primordial, such as 82Se, because of cosmic ray spallation, or via nuclear fission of uranium. Livermorium isotopes 290Lv through 293Lv have been discovered; the most stable livermorium isotope is 293Lv, which has a half-life of 0.061 seconds.[2][14]

With the exception of oxygen and livermorium, all chalcogens have at least one naturally occurring

radioisotope
, sulfur has trace 35S, selenium has 82Se, tellurium has 128Te and 130Te, and polonium has 210Po.

Among the lighter chalcogens (oxygen and sulfur), the most neutron-poor isotopes undergo

nuclear spins are more abundant in nature among the chalcogens selenium and tellurium than they are with sulfur.[16]

Allotropes

See also: Allotropes of oxygen and Allotropes of sulfur
Phase diagram of sulfur showing the relative stabilities of several allotropes[17]
The four stable chalcogens at STP
Phase diagram for solid oxygen

Oxygen's most common

allotrope is diatomic oxygen, or O2, a reactive paramagnetic molecule that is ubiquitous to aerobic organisms and has a blue color in its liquid state. Another allotrope is O3, or ozone, which is three oxygen atoms bonded together in a bent formation. There is also an allotrope called tetraoxygen, or O4,[18] and six allotropes of solid oxygen including "red oxygen", which has the formula O8.[19]

Sulfur has over 20 known allotropes, which is more than any other element except

monoclinic sulfur. Rhombic sulfur is the more stable of the two allotropes. Monoclinic sulfur takes the form of long needles and is formed when liquid sulfur is cooled to slightly below its melting point. The atoms in liquid sulfur are generally in the form of long chains, but above 190 °C, the chains begin to break down. If liquid sulfur above 190 °C is frozen very rapidly, the resulting sulfur is amorphous or "plastic" sulfur. Gaseous sulfur is a mixture of diatomic sulfur (S2) and 8-atom rings.[21]

Selenium has at least eight distinct allotropes.

amorphous allotropes, one of which is red and one of which is black.[23] The red allotrope converts to the black allotrope in the presence of heat. The gray allotrope of selenium is made from spirals on selenium atoms, while one of the red allotropes is made of stacks of selenium rings (Se8).[2][dubious – discuss
]

Tellurium is not known to have any allotropes,[24] although its typical form is hexagonal. Polonium has two allotropes, which are known as α-polonium and β-polonium.[25] α-polonium has a cubic crystal structure and converts to the rhombohedral β-polonium at 36 °C.[2]

The chalcogens have varying crystal structures. Oxygen's crystal structure is

hexagonal crystal structure, while polonium has a cubic crystal structure.[6][7]

Chemical

Oxygen, sulfur, and selenium are

electric polarizability several times lower than those of the other chalcogens.[16]

For

H3O+, a chalcogen forms three molecular orbitals arranged in a trigonal pyramidal
fashion and one lone pair. Double bonds are also common in chalcogen compounds, for example in chalcogenates (see below).

The

oxidation number is +6.[6] This oxidation number is found in sulfates, selenates, tellurates, polonates, and their corresponding acids, such as sulfuric acid
.

Oxygen is the most

metalloids to form oxides, including iron oxide, titanium oxide, and silicon oxide. Oxygen's most common oxidation state is −2, and the oxidation state −1 is also relatively common.[6] With hydrogen it forms water and hydrogen peroxide. Organic oxygen compounds are ubiquitous in organic chemistry
.

Sulfur's oxidation states are −2, +2, +4, and +6. Sulfur-containing analogs of oxygen compounds often have the prefix thio-. Sulfur's chemistry is similar to oxygen's, in many ways. One difference is that sulfur-sulfur double bonds are far weaker than oxygen-oxygen double bonds, but sulfur-sulfur single bonds are stronger than oxygen-oxygen single bonds.[29] Organic sulfur compounds such as thiols have a strong specific smell, and a few are utilized by some organisms.[2]

Selenium's oxidation states are −2, +4, and +6. Selenium, like most chalcogens, bonds with oxygen.

selenoproteins. Tellurium's oxidation states are −2, +2, +4, and +6.[6] Tellurium forms the oxides tellurium monoxide, tellurium dioxide, and tellurium trioxide.[2] Polonium's oxidation states are +2 and +4.[6]

Water dripping into a glass, showing drops and bubbles.
Water (H2O) is the most familiar chalcogen-containing compound.

There are many acids containing chalcogens, including sulfuric acid, sulfurous acid, selenic acid, and telluric acid. All hydrogen chalcogenides are toxic except for water.[30][31] Oxygen ions often come in the forms of oxide ions (O2−), peroxide ions (O2−2), and hydroxide ions (OH−). Sulfur ions generally come in the form of sulfides (S2−), bisulfides (SH−), sulfites (SO2−3), sulfates (SO2−4), and thiosulfates (S2O2−3). Selenium ions usually come in the form of selenides (Se2−), selenites (SeO2−3) and selenates (SeO2−4). Tellurium ions often come in the form of tellurates (TeO2−4).[6] Molecules containing metal bonded to chalcogens are common as minerals. For example, pyrite (FeS2) is an iron ore, and the rare mineral calaverite is the ditelluride (Au, Ag)Te2.

Although all group 16 elements of the periodic table, including oxygen, can be defined as chalcogens, oxygen and oxides are usually distinguished from chalcogens and chalcogenides. The term chalcogenide is more commonly reserved for sulfides, selenides, and tellurides, rather than for oxides.[32][33][34]

Except for polonium, the chalcogens are all fairly similar to each other chemically. They all form X2− ions when reacting with

electropositive metals.[28]

Sulfide minerals and analogous compounds produce gases upon reaction with oxygen.[35]

Compounds

With halogens

Chalcogens also form compounds with

anions.[33]

Organic

telluroketones. Out of these, thioketones are the most well-studied with 80% of chalcogenoketones papers being about them. Selenoketones make up 16% of such papers and telluroketones make up 4% of them. Thioketones have well-studied non-linear electric and photophysical properties. Selenoketones are less stable than thioketones and telluroketones are less stable than selenoketones. Telluroketones have the highest level of polarity of chalcogenoketones.[33]

With metals

There is a very large number of metal chalcogenides. There are also ternary compounds containing

dimers such as TiTl5Se8. Metal chalcogenide dimers also occur as lower tellurides, such as Zr5Te6.[33]

Elemental chalcogens react with certain lanthanide compounds to form lanthanide clusters rich in chalcogens.[

catalysts and stabilize nanoparticles.[33]

With pnictogens

Bismuth sulfide, a pnictogen chalcogenide

Compounds with chalcogen-

weak acids.[33] Binary compounds consisting of antimony or arsenic and a chalcogen. These compounds tend to be colorful and can be created by a reaction of the constituent elements at temperatures of 500 to 900 °C (932 to 1,652 °F).[38]

Other

Chalcogens form single bonds and double bonds with other carbon group elements than carbon, such as silicon, germanium, and tin. Such compounds typically form from a reaction of carbon group halides and chalcogenol salts or chalcogenol bases. Cyclic compounds with chalcogens, carbon group elements, and boron atoms exist, and occur from the reaction of boron dichalcogenates and carbon group metal halides. Compounds in the form of M-E, where M is silicon, germanium, or tin, and E is sulfur, selenium or tellurium have been discovered. These form when carbon group hydrides react or when heavier versions of carbenes react.[dubious – discuss] Sulfur and tellurium can bond with organic compounds containing both silicon and phosphorus.[33]

All of the chalcogens form

labile.[39] Also, oxygen can bond to hydrogen in a 1:1 ratio as in hydrogen peroxide, but this compound is unstable.[28]

Chalcogen compounds form a number of interchalcogens. For instance, sulfur forms the toxic sulfur dioxide and sulfur trioxide.[28] Tellurium also forms oxides. There are some chalcogen sulfides as well. These include selenium sulfide, an ingredient in some shampoos.[7]

Since 1990, a number of borides with chalcogens bonded to them have been detected. The chalcogens in these compounds are mostly sulfur, although some do contain selenium instead. One such chalcogen boride consists of two molecules of dimethyl sulfide attached to a boron-hydrogen molecule. Other important boron-chalcogen compounds include macropolyhedral systems. Such compounds tend to feature sulfur as the chalcogen. There are also chalcogen borides with two, three, or four chalcogens. Many of these contain sulfur but some, such as Na2B2Se7 contain selenium instead.[40]

History

Early discoveries

Sulfur has been known since

Louis-Jacques Thénard proved sulfur to be a chemical element.[2]

Early attempts to separate oxygen from air were hampered by the fact that air was thought of as a single element up to the 17th and 18th centuries.

mercuric oxide and collected the resulting gas. Carl Wilhelm Scheele had also created oxygen in 1771 by the same method, but Scheele did not publish his results until 1777.[2]

Tellurium was first discovered in 1783 by

Martin Klaproth, who purified the undiscovered element. Klaproth decided to call the element tellurium after the Latin word for earth.[2]

Selenium was discovered in 1817 by Jöns Jacob Berzelius. Berzelius noticed a reddish-brown sediment at a sulfuric acid manufacturing plant. The sample was thought to contain arsenic. Berzelius initially thought that the sediment contained tellurium, but came to realize that it also contained a new element, which he named selenium after the Greek moon goddess Selene.[2][41]

Periodic table placing

Dmitri Mendeleev's periodic system proposed in 1871 showing oxygen, sulfur, selenium and tellurium part of his group VI

Three of the chalcogens (sulfur, selenium, and tellurium) were part of the discovery of

John Newlands produced a series of papers where he listed the elements in order of increasing atomic weight and similar physical and chemical properties that recurred at intervals of eight; he likened such periodicity to the octaves of music.[42][43] His version included a "group b" consisting of oxygen, sulfur, selenium, tellurium, and osmium
.

Johann Wolfgang Döbereiner was among the first to notice similarities between what are now known as chalcogens.

After 1869, Dmitri Mendeleev proposed his periodic table placing oxygen at the top of "group VI" above sulfur, selenium, and tellurium.[44] Chromium, molybdenum, tungsten, and uranium were sometimes included in this group, but they would be later rearranged as part of group VIB; uranium would later be moved to the actinide series. Oxygen, along with sulfur, selenium, tellurium, and later polonium would be grouped in group VIA, until the group's name was changed to group 16 in 1988.[45]

Modern discoveries

In the late 19th century,

pitchblende was emitting four times as much radioactivity as could be explained by the presence of uranium alone. The Curies gathered several tons of pitchblende and refined it for several months until they had a pure sample of polonium. The discovery officially took place in 1898. Prior to the invention of particle accelerators, the only way to produce polonium was to extract it over several months from uranium ore.[2]

The first attempt at creating livermorium was from 1976 to 1977 at the

LBNL, who bombarded curium-248 with calcium-48, but were not successful. After several failed attempts in 1977, 1998, and 1999 by research groups in Russia, Germany, and the US, livermorium was created successfully in 2000 at the Joint Institute for Nuclear Research by bombarding curium-248 atoms with calcium-48 atoms. The element was known as ununhexium until it was officially named livermorium in 2012.[2]

Names and etymology

In the 19th century,

amphid salts (salts of oxyacids.[47][48] Formerly regarded as composed of two oxides, an acid and a basic oxide) The term received some use in the early 1800s but is now obsolete.[46] The name chalcogen comes from the Greek words χαλκος (chalkos, literally "copper"), and γενές (genes, born,[49] gender, kindle). It was first used in 1932 by Wilhelm Biltz's group at Leibniz University Hannover, where it was proposed by Werner Fischer.[32] The word "chalcogen" gained popularity in Germany during the 1930s because the term was analogous to "halogen".[50] Although the literal meanings of the modern Greek words imply that chalcogen means "copper-former", this is misleading because the chalcogens have nothing to do with copper in particular. "Ore-former" has been suggested as a better translation,[51] as the vast majority of metal ores are chalcogenides and the word χαλκος in ancient Greek was associated with metals and metal-bearing rock in general; copper, and its alloy bronze
, was one of the first metals to be used by humans.

Oxygen's name comes from the Greek words oxy genes, meaning "acid-forming". Sulfur's name comes from either the Latin word sulfurium or the Sanskrit word sulvere; both of those terms are ancient words for sulfur. Selenium is named after the Greek goddess of the moon, Selene, to match the previously discovered element tellurium, whose name comes from the Latin word telus, meaning earth. Polonium is named after Marie Curie's country of birth, Poland.[7] Livermorium is named for the Lawrence Livermore National Laboratory.[52]

Occurrence

The four lightest chalcogens (oxygen, sulfur, selenium, and tellurium) are all

copper ores and selenium and tellurium occur in small traces in such ores.[28] Polonium
forms naturally from the decay of other elements, even though it is not primordial. Livermorium does not occur naturally at all.

Oxygen makes up 21% of the atmosphere by weight, 89% of water by weight, 46% of the Earth's crust by weight,

hydroxide minerals, and in numerous other mineral groups.[54] Stars of at least eight times the mass of the Sun also produce oxygen in their cores via nuclear fusion.[12] Oxygen is the third-most abundant element in the universe, making up 1% of the universe by weight.[55][56]

Sulfur makes up 0.035% of the Earth's crust by weight, making it the 17th most abundant element there

sulfosalt minerals.[54] Stars of at least 12 times the mass of the Sun produce sulfur in their cores via nuclear fusion.[12] Sulfur is the tenth most abundant element in the universe, making up 500 parts per million of the universe by weight.[55][56]

Selenium makes up 0.05

nanogram of selenium per cubic meter. There are mineral groups known as selenates and selenites, but there are not many minerals in these groups.[57] Selenium is not produced directly by nuclear fusion.[12] Selenium makes up 30 parts per billion of the universe by weight.[56]

There are only 5 parts per billion of tellurium in the Earth's crust and 15 parts per billion of tellurium in seawater.[2] Tellurium is one of the eight or nine least abundant elements in the Earth's crust.[7] There are a few dozen tellurate minerals and telluride minerals, and tellurium occurs in some minerals with gold, such as sylvanite and calaverite.[58] Tellurium makes up 9 parts per billion of the universe by weight.[7][56][59]

Polonium only occurs in trace amounts on Earth, via radioactive decay of uranium and thorium. It is present in uranium ores in concentrations of 100 micrograms per metric ton. Very minute amounts of polonium exist in the soil and thus in most food, and thus in the human body.[2] The Earth's crust contains less than 1 part per billion of polonium, making it one of the ten rarest metals on Earth.[2][6]

Livermorium is always produced artificially in particle accelerators. Even when it is produced, only a small number of atoms are synthesized at a time.

Chalcophile elements

See also:
Chalcophile and Goldschmidt classification

Chalcophile elements are those that remain on or close to the surface because they combine readily with chalcogens other than oxygen, forming compounds which do not sink into the core. Chalcophile ("chalcogen-loving") elements in this context are those metals and heavier nonmetals that have a low affinity for oxygen and prefer to bond with the heavier chalcogen sulfur as sulfides.

lithophile elements,[54] chalcophile elements separated below the lithophiles at the time of the first crystallisation of the Earth's crust. This has led to their depletion in the Earth's crust relative to their solar abundances, though this depletion has not reached the levels found with siderophile elements.[61]

Goldschmidt classification in the periodic table
1 2 3 4 5 6 7 8 9 10 11 12 13 14
15
 16 17 18
Group →
↓ Period
1 1
H 		2
He
2 3
Li 		4
Be 		5
B 		6
C 		7
N 		8
O 		9
F 		10
Ne
3 11
Na 		12
Mg 		13
Al 		14
Si 		15
P 		16
S 		17
Cl 		18
Ar
4 19
K 		20
Ca 		21
Sc 		22
Ti 		23
V 		24
Cr 		25
Mn 		26
Fe 		27
Co 		28
Ni 		29
Cu 		30
Zn 		31
Ga 		32
Ge 		33
As 		34
Se 		35
Br 		36
Kr
5 37
Rb 		38
Sr 		39
Y 		40
Zr 		41
Nb 		42
Mo 		43
Tc 		44
Ru 		45
Rh 		46
Pd 		47
Ag 		48
Cd 		49
In 		50
Sn 		51
Sb 		52
Te 		53
I 		54
Xe
6 55
Cs 		56
Ba 		1 asterisk 71
Lu 		72
Hf 		73
Ta 		74
W 		75
Re 		76
Os 		77
Ir 		78
Pt 		79
Au 		80
Hg 		81
Tl 		82
Pb 		83
Bi 		84
Po 		85
At 		86
Rn
7 87
Fr 		88
Ra 		1 asterisk 103
Lr 		104
Rf 		105
Db 		106
Sg 		107
Bh 		108
Hs 		109
Mt 		110
Ds 		111
Rg 		112
Cn 		113
Nh 		114
Fl 		115
Mc 		116
Lv 		117
Ts 		118
Og
 
1 asterisk 57
La 		58
Ce 		59
Pr 		60
Nd 		61
Pm 		62
Sm 		63
Eu 		64
Gd 		65
Tb 		66
Dy 		67
Ho 		68
Er 		69
Tm 		70
Yb
1 asterisk 89
Ac 		90
Th 		91
Pa 		92
U 		93
Np 		94
Pu 		95
Am 		96
Cm 		97
Bk 		98
Cf 		99
Es 		100
Fm 		101
Md 		102
No

Production

Approximately 100 million metric tons of oxygen are produced yearly. Oxygen is most commonly produced by fractional distillation, in which air is cooled to a liquid, then warmed, allowing all the components of air except for oxygen to turn to gases and escape. Fractionally distilling air several times can produce 99.5% pure oxygen.[62] Another method with which oxygen is produced is to send a stream of dry, clean air through a bed of molecular sieves made of zeolite, which absorbs the nitrogen in the air, leaving 90 to 93% pure oxygen.[2]

Sulfur recovered from oil refining in Alberta, stockpiled for shipment in North Vancouver, British Columbia

Sulfur can be mined in its elemental form, although this method is no longer as popular as it used to be. In 1865 a large deposit of elemental sulfur was discovered in the U.S. states of Louisiana and Texas, but it was difficult to extract at the time. In the 1890s, Herman Frasch came up with the solution of liquefying the sulfur with superheated steam and pumping the sulfur up to the surface. These days sulfur is instead more often extracted from oil, natural gas, and tar.[2]

The world production of selenium is around 1500 metric tons per year, out of which roughly 10% is recycled. Japan is the largest producer, producing 800 metric tons of selenium per year. Other large producers include Belgium (300 metric tons per year), the United States (over 200 metric tons per year), Sweden (130 metric tons per year), and Russia (100 metric tons per year). Selenium can be extracted from the waste from the process of electrolytically refining copper. Another method of producing selenium is to farm selenium-gathering plants such as

milk vetch. This method could produce three kilograms of selenium per acre, but is not commonly practiced.[2]

Tellurium is mostly produced as a by-product of the processing of copper.

electrolytic reduction of sodium telluride. The world production of tellurium is between 150 and 200 metric tons per year. The United States is one of the largest producers of tellurium, producing around 50 metric tons per year. Peru, Japan, and Canada are also large producers of tellurium.[2]

Until the creation of nuclear reactors, all polonium had to be extracted from uranium ore. In modern times, most

St. Petersburg for distribution. The United States is the largest consumer of polonium.[2]

All livermorium is produced artificially in particle accelerators. The first successful production of livermorium was achieved by bombarding curium-248 atoms with calcium-48 atoms. As of 2011, roughly 25 atoms of livermorium had been synthesized.[2]

Applications

rocket fuel (in liquid form), and metal cutting.[2]

Most sulfur produced is transformed into

vulcanize it. Sulfur is used in some types of concrete and fireworks. 60% of all sulfuric acid produced is used to generate phosphoric acid.[2][65] Sulfur is used as a pesticide (specifically as an acaricide and fungicide) on "orchard, ornamental, vegetable, grain, and other crops."[66]

Gunpowder, an application of sulfur

Around 40% of all selenium produced goes to

photovoltaic materials claim 10% of all selenium produced. Pigments account for 5% of all selenium produced. Historically, machines such as photocopiers and light meters used one-third of all selenium produced, but this application is in steady decline.[2]

vulcanized rubber. Cadmium telluride is used as a high-efficiency material in solar panels.[2]

Some of polonium's applications relate to the element's radioactivity. For instance, polonium is used as an alpha-particle generator for research. Polonium alloyed with beryllium provides an efficient neutron source. Polonium is also used in nuclear batteries. Most polonium is used in antistatic devices.[2][6] Livermorium does not have any uses whatsoever due to its extreme rarity and short half-life.

Organochalcogen compounds are involved in the

synthetic chemistry. Metallic redox centers of biological importance are tunable by interactions of ligands containing chalcogens, such as methionine and selenocysteine. Also, chalcogen through-bonds[dubious – discuss] can provide insight about the process of electron transfer.[16]

Biological role

Main articles: Dioxygen in biological reactions, Sulfur cycle, and Selenium in biology
DNA, an important biological compound containing oxygen

Oxygen is needed by almost all organisms for the purpose of generating ATP. It is also a key component of most other biological compounds, such as water, amino acids and DNA. Human blood contains a large amount of oxygen. Human bones contain 28% oxygen. Human tissue contains 16% oxygen. A typical 70-kilogram human contains 43 kilograms of oxygen, mostly in the form of water.[2]

All animals need significant amounts of sulfur. Some amino acids, such as cysteine and methionine contain sulfur. Plant roots take up sulfate ions from the soil and reduce it to sulfide ions. Metalloproteins also use sulfur to attach to useful metal atoms in the body and sulfur similarly attaches itself to poisonous metal atoms like cadmium to haul them to the safety of the liver. On average, humans consume 900 milligrams of sulfur each day. Sulfur compounds, such as those found in skunk spray often have strong odors.[2]

All animals and some plants need trace amounts of

heavy metal poisoning.[67]

Tellurium is not known to be needed for animal life, although a few fungi can incorporate it in compounds in place of selenium. Microorganisms also absorb tellurium and emit

parts per million of tellurium in dry weight.[2]

Polonium has no biological role, and is highly toxic on account of being radioactive.

Toxicity

NFPA 704
fire diamond
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
0
0
Fire diamond for selenium

Oxygen is generally nontoxic, but oxygen toxicity has been reported when it is used in high concentrations. In both elemental gaseous form and as a component of water, it is vital to almost all life on Earth. Despite this, liquid oxygen is highly dangerous.[7] Even gaseous oxygen is dangerous in excess. For instance, sports divers have occasionally drowned from convulsions caused by breathing pure oxygen at a depth of more than 10 meters (33 feet) underwater.[2] Oxygen is also toxic to some bacteria.[53] Ozone, an allotrope of oxygen, is toxic to most life. It can cause lesions in the respiratory tract.[68]

Sulfur is generally nontoxic and is even a vital nutrient for humans. However, in its elemental form it can cause redness in the eyes and skin, a burning sensation and a cough if inhaled, a burning sensation and diarrhoea and/or

catharsis[66] if ingested, and can irritate the mucous membranes.[69][70] An excess of sulfur can be toxic for cows because microbes in the rumens of cows produce toxic hydrogen sulfide upon reaction with sulfur.[71] Many sulfur compounds, such as hydrogen sulfide (H2S) and sulfur dioxide (SO2) are highly toxic.[2]

Selenium is a trace nutrient required by humans on the order of tens or hundreds of micrograms per day. A dose of over 450 micrograms can be toxic, resulting in bad breath and body odor. Extended, low-level exposure, which can occur at some industries, results in weight loss, anemia, and dermatitis. In many cases of selenium poisoning, selenous acid is formed in the body.[72] Hydrogen selenide (H2Se) is highly toxic.[2]

Exposure to tellurium can produce unpleasant side effects. As little as 10 micrograms of tellurium per cubic meter of air can cause notoriously unpleasant breath, described as smelling like rotten garlic.[7] Acute tellurium poisoning can cause vomiting, gut inflammation, internal bleeding, and respiratory failure. Extended, low-level exposure to tellurium causes tiredness and indigestion. Sodium tellurite (Na2TeO3) is lethal in amounts of around 2 grams.[2]

Polonium is dangerous as an

lymphopenia. It can also damage hair follicles and white blood cells.[2][73] Polonium-210 is only dangerous if ingested or inhaled because its alpha particle emissions cannot penetrate human skin.[64] Polonium-209 is also toxic, and can cause leukemia.[74]

Amphid salts

Amphid salts was a name given by

Jons Jacob Berzelius in the 19th century for chemical salts derived from the 16th group of the periodic table which included oxygen, sulfur, selenium, and tellurium.[75] The term received some use in the early 1800s but is now obsolete.[76]
The current term in use for the 16th group is chalcogens.

See also

References

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External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Chalcogen&oldid=1214870237"