The chalcogens (ore forming) ( ) are the
chemical element
A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its ...
s in
group 16 of the
periodic table
The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows (" periods") and columns (" groups"). It is an icon of chemistry and is widely used in physics and other s ...
. This group is also known as the oxygen family. Group 16 consists of the elements
oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
(O),
sulfur
Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
(S),
selenium
Selenium is a chemical element; it has symbol (chemistry), symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elem ...
(Se),
tellurium
Tellurium is a chemical element; it has symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally fou ...
(Te), and the
radioactive
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...
elements
polonium
Polonium is a chemical element; it has symbol Po and atomic number 84. A rare and highly radioactive metal (although sometimes classified as a metalloid) with no stable isotopes, polonium is a chalcogen and chemically similar to selenium and tel ...
(Po) and
livermorium
Livermorium is a synthetic chemical element; it has symbol Lv and atomic number 116. It is an extremely radioactive element that has only been created in a laboratory setting and has not been observed in nature. The element is named after the La ...
(Lv).
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 () principally meaning
copper
Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
(the term was also used for
bronze
Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals (such as phosphorus) or metalloid ...
,
brass
Brass is an alloy of copper and zinc, in proportions which can be varied to achieve different colours and mechanical, electrical, acoustic and chemical properties, but copper typically has the larger proportion, generally copper and zinc. I ...
, any metal in the poetic sense,
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration ...
and
coin
A coin is a small object, usually round and flat, used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in large quantities at a mint in order to facilitate trade. They are most often issued by ...
),
and the Latinized Greek word , meaning ''born'' or ''produced''.
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 electron
In chemistry and physics, valence electrons are electrons in the outermost shell of an atom, and that can participate in the formation of a chemical bond if the outermost shell is not closed. In a single covalent bond, a shared pair forms with b ...
s, leaving them two electrons short of a full outer shell. Their most common
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...
s are −2, +2, +4, and +6. They have relatively low
atomic radii, especially the lighter ones.
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
Selenocysteine (symbol Sec or U, in older publications also as Se-Cys) is the 21st proteinogenic amino acid. Selenoproteins contain selenocysteine residues. Selenocysteine is an analogue of the more common cysteine with selenium in place of the ...
) but is also commonly toxic.
Tellurium often has unpleasant effects (although
some organisms can use it), and polonium (especially the
isotope
Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...
polonium-210
Polonium-210 (210Po, Po-210, historically radium F) is an isotope of polonium. It undergoes alpha decay to stable 206Pb with a half-life of 138.376 days (about months), the longest half-life of all naturally occurring polonium isotopes (210– ...
) is always harmful as a result of its radioactivity.
Sulfur has more than 20
allotrope
Allotropy or allotropism () is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element: the ...
s, 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
The carbon group is a group (periodic table), periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). It lies within the p-block.
In modern International Union of Pure and Applied Ch ...
elements.
Oxygen is generally obtained by
separation of air into nitrogen and oxygen. 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
Steelmaking is the process of producing steel from iron ore and/or scrap. Steel has been made for millennia, and was commercialized on a massive scale in the 1850s and 1860s, using the Bessemer process, Bessemer and open hearth furnace, Siemens-M ...
. Sulfur is mostly converted into
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
, which is heavily used in the chemical industry.
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.
Properties
Atomic and physical
Chalcogens show similar patterns in
electron configuration
In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon ato ...
, especially in the outermost
shells, where they all have the same number of
valence electron
In chemistry and physics, valence electrons are electrons in the outermost shell of an atom, and that can participate in the formation of a chemical bond if the outermost shell is not closed. In a single covalent bond, a shared pair forms with b ...
s, resulting in similar trends in chemical behavior:
All chalcogens have six
valence electron
In chemistry and physics, valence electrons are electrons in the outermost shell of an atom, and that can participate in the formation of a chemical bond if the outermost shell is not closed. In a single covalent bond, a shared pair forms with b ...
s. All of the solid, stable chalcogens are soft and do not
conduct heat well.
Electronegativity
Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...
decreases towards the chalcogens with higher atomic numbers. Density, melting and boiling points, and
atomic and
ionic radii tend to increase towards the chalcogens with higher atomic numbers.
Isotopes
Out of the six known chalcogens, one (oxygen) has an atomic number equal to a nuclear
magic number, which means that their
atomic nuclei
The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford at the University of Manchester based on the 1909 Geiger–Marsden gold foil experiment. Aft ...
tend to have increased stability against radioactive decay.
Oxygen has three stable isotopes, and 14 unstable ones. Sulfur has four stable isotopes, 20 radioactive ones, and one
isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...
. Selenium has six
observationally stable
Stable nuclides are isotopes of a chemical element whose nucleons are in a configuration that does not permit them the surplus energy required to produce a radioactive emission. The nuclei of such isotopes are not radioactive and unlike radionuc ...
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. It has an additional 28 isomers.
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
Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the ...
spallation, or via
nuclear fission
Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactiv ...
of uranium. Livermorium isotopes
288Lv through
293Lv have been discovered; the most stable livermorium isotope is
293Lv, which has a half-life of 0.061 seconds.
With the exception of livermorium, all chalcogens have at least one naturally occurring
radioisotope
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...
: oxygen has trace
15O, 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
proton emission
Proton emission (also known as proton radioactivity) is a rare type of radioactive decay in which a proton is ejected from a atomic nucleus, nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay ...
, the moderately neutron-poor isotopes undergo
electron capture
Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Th ...
or
β+ decay, the moderately neutron-rich isotopes undergo
β− decay, and the most neutron rich isotopes undergo
neutron emission
Neutron emission is a mode of radioactive decay in which one or more neutrons are ejected from a Atomic nucleus, nucleus. It occurs in the most neutron-rich/proton-deficient nuclides, and also from excited states of other nuclides as in photodisin ...
. The middle chalcogens (selenium and tellurium) have similar decay tendencies as the lighter chalcogens, but no proton-emitting isotopes have been observed, and some of the most neutron-deficient isotopes of tellurium undergo
alpha decay
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus). The parent nucleus transforms or "decays" into a daughter product, with a mass number that is reduced by four and an a ...
. Polonium isotopes tend to decay via alpha or beta decay. Isotopes with nonzero
nuclear spin
Nuclear may refer to:
Physics
Relating to the nucleus of the atom:
* Nuclear engineering
* Nuclear physics
* Nuclear power
* Nuclear reactor
* Nuclear weapon
* Nuclear medicine
*Radiation therapy
*Nuclear warfare
Mathematics
* Nuclear space
* ...
s are more abundant in nature among the chalcogens selenium and tellurium than they are with sulfur.
Allotropes
Oxygen's most common
allotrope
Allotropy or allotropism () is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element: the ...
is diatomic oxygen, or O
2, a reactive paramagnetic molecule that is ubiquitous to
aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment. The ability to exhibit aerobic respiration may yield benefits to the aerobic organism, as aerobic respiration yields more energy than anaerobic ...
s and has a blue color in its
liquid state. Another allotrope is O
3, or
ozone
Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...
, which is three oxygen atoms bonded together in a bent formation. There is also an allotrope called
tetraoxygen, or O
4, and six allotropes of
solid oxygen including "red oxygen", which has the formula O
8.
Sulfur has over 20 known allotropes, which is more than any other element except
carbon
Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
.
The most common allotropes are in the form of eight-atom rings, but other molecular allotropes that contain as few as two atoms or as many as 20 are known. Other notable sulfur allotropes include
rhombic sulfur and
monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...
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 (S
2) and 8-atom rings.
Selenium has at least eight distinct allotropes. The gray allotrope, commonly referred to as the "metallic" allotrope, despite not being a metal, is stable and has a hexagonal
crystal structure
In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...
. The gray allotrope of selenium is soft, with a
Mohs hardness
The Mohs scale ( ) of mineral hardness is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fair ...
of 2, and brittle. Four other allotropes of selenium are
metastable
In chemistry and physics, metastability is an intermediate energetic state within a dynamical system other than the system's state of least energy.
A ball resting in a hollow on a slope is a simple example of metastability. If the ball is onl ...
. These include two
monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...
red allotropes and two
amorphous
In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid) is a solid that lacks the long-range order that is a characteristic of a crystal. The terms "glass" and "glassy solid" are sometimes used synonymousl ...
allotropes, one of which is red and one of which is black. The red allotrope converts to the black allotrope in the presence of heat. The gray allotrope of selenium is made from
spiral
In mathematics, a spiral is a curve which emanates from a point, moving further away as it revolves around the point. It is a subtype of whorled patterns, a broad group that also includes concentric objects.
Two-dimensional
A two-dimension ...
s on selenium atoms, while one of the red allotropes is made of stacks of selenium rings (Se
8).
Tellurium is not known to have any allotropes, although its typical form is hexagonal. Polonium has two allotropes, which are known as α-polonium and β-polonium. α-polonium has a cubic crystal structure and converts to the rhombohedral β-polonium at 36 °C.
The chalcogens have varying crystal structures. Oxygen's crystal structure is
monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...
, sulfur's is
orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...
, selenium and tellurium have the
hexagonal
In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°.
Regular hexagon
A regular hexagon is d ...
crystal structure, while polonium has a
cubic crystal structure.
Chemical
Oxygen, sulfur, and selenium are
nonmetal
In the context of the periodic table, a nonmetal is a chemical element that mostly lacks distinctive metallic properties. They range from colorless gases like hydrogen to shiny crystals like iodine. Physically, they are usually lighter (less ...
s, and tellurium is a
metalloid
A metalloid is a chemical element which has a preponderance of material property, properties in between, or that are a mixture of, those of metals and Nonmetal (chemistry), nonmetals. The word metalloid comes from the Latin language, Latin ''meta ...
, meaning that its chemical properties are between those of a
metal
A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated wit ...
and those of a nonmetal.
It is not certain whether polonium is a metal or a metalloid. Some sources refer to polonium as a metalloid,
although it has some metallic properties. Also, some allotropes of selenium display characteristics of a metalloid, even though selenium is usually considered a nonmetal. Even though oxygen is a chalcogen, its chemical properties are different from those of other chalcogens. One reason for this is that the heavier chalcogens have vacant
d-orbitals. Oxygen's electronegativity is also much higher than those of the other chalcogens. This makes oxygen's
electric polarizability several times lower than those of the other chalcogens.
For
covalent bond
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...
ing a chalcogen may accept two electrons according to the
octet rule
The octet rule is a chemical rule of thumb that reflects the theory that main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. The ru ...
, leaving two
lone pair
In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bondIUPAC ''Gold Book'' definition''lone (electron) pair''/ref> and is sometimes called an unshared pair or non-bonding pair. Lone ...
s. When an atom forms two
single bonds, they
form an angle between 90° and 120°. In 1+
cation
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s, such as
, 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
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to other atoms are fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. Concep ...
of the most common chalcogen compounds with positive metals is −2. However the tendency for chalcogens to form compounds in the −2 state decreases towards the heavier chalcogens.
Other oxidation numbers, such as −1 in
pyrite
The mineral pyrite ( ), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic luster and pale brass-yellow hue ...
and
peroxide
In chemistry, peroxides are a group of Chemical compound, compounds with the structure , where the R's represent a radical (a portion of a complete molecule; not necessarily a free radical) and O's are single oxygen atoms. Oxygen atoms are joined ...
, do occur. The highest formal
oxidation number
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to other atoms are fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. Concep ...
is +6.
This oxidation number is found in
sulfate
The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...
s,
selenates,
tellurate
In chemistry, tellurate is a compound containing an oxyanion of tellurium where tellurium has an oxidation number of +6. In the naming of inorganic compounds it is a suffix that indicates a polyatomic ion, polyatomic anion with a central telluri ...
s, polonates, and their corresponding acids, such as
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
.
Oxygen is the most
electronegative
Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the d ...
element except for
fluorine
Fluorine is a chemical element; it has Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard temperature and pressure, standard conditions as pale yellow Diatomic molecule, diatomic gas. Fluorine is extre ...
, and forms compounds with almost all of the chemical elements, including some of the
noble gas
The noble gases (historically the inert gases, sometimes referred to as aerogens) are the members of Group (periodic table), group 18 of the periodic table: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn) and, in some ...
es. It commonly bonds with many metals and
metalloids
A metalloid is a chemical element which has a preponderance of properties in between, or that are a mixture of, those of metals and nonmetals. The word metalloid comes from the Latin ''metallum'' ("metal") and the Greek ''oeides'' ("resembling ...
to form
oxide
An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...
s, including
iron oxide
An iron oxide is a chemical compound composed of iron and oxygen. Several iron oxides are recognized. Often they are non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is rust.
Iron ...
,
titanium oxide
Titanium oxide may refer to:
* Titanium dioxide (titanium(IV) oxide), TiO2
* Titanium(II) oxide (titanium monoxide), TiO, a non-stoichiometric oxide
* Titanium(III) oxide (dititanium trioxide), Ti2O3
* Ti3O
* Ti2O
* δ-TiOx (x= 0.68–0.75)
* Ti ...
, and
silicon oxide. Oxygen's most common
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...
is −2, and the oxidation state −1 is also relatively common.
With
hydrogen
Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
it forms water and
hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...
. Organic oxygen compounds are ubiquitous in
organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...
.
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 bond
In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...
s are far weaker than oxygen-oxygen double bonds, but sulfur-sulfur
single bonds are stronger than oxygen-oxygen single bonds. Organic sulfur compounds such as
thiol
In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...
s have a strong specific smell, and a few are utilized by some organisms.
Selenium's oxidation states are −2, +4, and +6. Selenium, like most chalcogens, bonds with oxygen.
There are some
organic selenium compounds, such as
selenoproteins In molecular biology a selenoprotein is any protein that includes a selenocysteine (Sec, U, Se-Cys) amino acid residue. Among functionally characterized selenoproteins are five glutathione peroxidases (GPX) and three thioredoxin reductases, (TrxR/TX ...
. Tellurium's oxidation states are −2, +2, +4, and +6.
Tellurium forms the oxides
tellurium monoxide,
tellurium dioxide, and
tellurium trioxide.
Polonium's oxidation states are +2 and +4.
There are many acids containing chalcogens, including sulfuric acid,
sulfurous acid
Sulfuric(IV) acid (United Kingdom spelling: sulphuric(IV) acid), also known as sulfurous (UK: sulphurous) acid and thionic acid, is the chemical compound with the chemical formula, formula .
Raman spectroscopy, Raman spectra of solutions o ...
,
selenic acid, and
telluric acid
Telluric acid, or more accurately orthotelluric acid, is a chemical compound with the formula , often written as . It is a white crystalline solid made up of octahedral molecules which persist in aqueous solution. In the solid state, there are ...
. All
hydrogen chalcogenides are toxic except for
water
Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
.
Oxygen ions often come in the forms of
oxide
An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...
ions (),
peroxide
In chemistry, peroxides are a group of Chemical compound, compounds with the structure , where the R's represent a radical (a portion of a complete molecule; not necessarily a free radical) and O's are single oxygen atoms. Oxygen atoms are joined ...
ions (), and
hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It ...
ions (). Sulfur ions generally come in the form of
sulfide
Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...
s (),
bisulfide
Bisulfide (or bisulphide in British English) is an inorganic anion with the chemical formula HS− (also written as SH−). It contributes no color to bisulfide salts, and its salts may have a distinctive putrid smell. It is a strong base. Bisul ...
s (),
sulfite
Sulfites or sulphites are compounds that contain the sulfite ion (systematic name: sulfate(IV) ion), . The sulfite ion is the conjugate base of bisulfite. Although its acid (sulfurous acid) is elusive, its salts are widely used.
Sulfites are ...
s (),
sulfate
The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...
s (), and
thiosulfate
Thiosulfate ( IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula . Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, ...
s (). Selenium ions usually come in the form of
selenide
A selenide is a chemical compound containing a selenium with oxidation number of −2. Similar to sulfide, selenides occur both as inorganic compounds and as organic derivatives, which are called organoselenium compound.
Inorganic selenides
Th ...
s (),
selenites () and
selenates (). Tellurium ions often come in the form of
tellurate
In chemistry, tellurate is a compound containing an oxyanion of tellurium where tellurium has an oxidation number of +6. In the naming of inorganic compounds it is a suffix that indicates a polyatomic ion, polyatomic anion with a central telluri ...
s ().
Molecules containing metal bonded to chalcogens are common as minerals. For example,
pyrite
The mineral pyrite ( ), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic luster and pale brass-yellow hue ...
(FeS
2) is an
iron ore
Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the f ...
, and the rare mineral
calaverite is the ditelluride .
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
chalcogenide
: 220px, Cadmium sulfide, a prototypical metal chalcogenide, is used as a yellow pigment.
A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elemen ...
s. The term ''chalcogenide'' is more commonly reserved for
sulfide
Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...
s,
selenide
A selenide is a chemical compound containing a selenium with oxidation number of −2. Similar to sulfide, selenides occur both as inorganic compounds and as organic derivatives, which are called organoselenium compound.
Inorganic selenides
Th ...
s, and
tellurides, rather than for
oxide
An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...
s.
Except for polonium, the chalcogens are all fairly similar to each other chemically. They all form X
2− ions when reacting with
electropositive
Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the d ...
metals.
Sulfide mineral
The sulfide minerals are a class of minerals containing sulfide (S2−) or disulfide () as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenide mineral, selenides, the tell ...
s and analogous compounds produce gases upon reaction with oxygen.
Compounds
With halogens
Chalcogens also form compounds with
halogen
The halogens () are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors would ...
s known as chalcohalides, or chalcogen halides. The majority of simple chalcogen halides are well-known and widely used as chemical
reagent
In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...
s. However, more complicated chalcogen halides, such as sulfenyl, sulfonyl, and sulfuryl halides, are less well known to science. Out of the compounds consisting purely of chalcogens and halogens, there are a total of 13 chalcogen fluorides, nine chalcogen chlorides, eight chalcogen bromides, and six chalcogen iodides that are known. The heavier chalcogen halides often have significant molecular interactions. Sulfur fluorides with low valences are fairly unstable and little is known about their properties. However, sulfur fluorides with high valences, such as
sulfur hexafluoride
Sulfur hexafluoride or sulphur hexafluoride ( British spelling) is an inorganic compound with the formula SF6. It is a colorless, odorless, non-flammable, and non-toxic gas. has an octahedral geometry, consisting of six fluorine atoms attache ...
, are stable and well-known.
Sulfur tetrafluoride is also a well-known sulfur fluoride. Certain selenium fluorides, such as
selenium difluoride, have been produced in small amounts. The crystal structures of both
selenium tetrafluoride
Selenium tetrafluoride ( Se F4) is an inorganic compound. It is a colourless liquid that reacts readily with water. It can be used as a fluorinating reagent in organic syntheses (fluorination of alcohols, carboxylic acids or carbonyl compounds) an ...
and
tellurium tetrafluoride are known. Chalcogen chlorides and bromides have also been explored. In particular, selenium dichloride and sulfur dichloride can react to form
organic selenium compounds. Dichalcogen dihalides, such as Se
2Cl
2 also are known to exist. There are also mixed chalcogen-halogen compounds. These include SeSX, with X being chlorine or bromine. Such compounds can form in mixtures of
sulfur dichloride and selenium halides. These compounds have been fairly recently structurally characterized, as of 2008. In general, diselenium and disulfur chlorides and bromides are useful chemical reagents. Chalcogen halides with attached metal atoms are soluble in organic solutions. One example of such a compound is . Unlike selenium chlorides and bromides, selenium
iodides have not been isolated, as of 2008, although it is likely that they occur in solution. Diselenium diiodide, however, does occur in equilibrium with selenium atoms and iodine molecules. Some tellurium halides with low valences, such as and , form
polymer
A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...
s when in the
solid state. These tellurium halides can be synthesized by the reduction of pure tellurium with
superhydride and reacting the resulting product with tellurium tetrahalides. Ditellurium dihalides tend to get less stable as the halides become lower in atomic number and atomic mass. Tellurium also forms iodides with even fewer iodine atoms than diiodides. These include TeI and Te
2I. These compounds have extended structures in the solid state. Halogens and chalcogens can also form halochalcogenate
anion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
s.
Organic
Alcohol
Alcohol may refer to:
Common uses
* Alcohol (chemistry), a class of compounds
* Ethanol, one of several alcohols, commonly known as alcohol in everyday life
** Alcohol (drug), intoxicant found in alcoholic beverages
** Alcoholic beverage, an alco ...
s,
phenol
Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile and can catch fire.
The molecule consists of a phenyl group () ...
s and other similar compounds contain oxygen. However, in
thiol
In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...
s,
selenols and
tellurol
Tellurols are analogues of alcohol (chemistry), alcohols and phenols where tellurium replaces oxygen. Tellurols, selenols, and thiols have similar properties, but tellurols are the least stable. Although they are fundamental representatives of orga ...
s; sulfur, selenium, and tellurium replace oxygen. Thiols are better known than selenols or tellurols. Aside from alcohols, thiols are the most stable chalcogenols and tellurols are the least stable, being unstable in heat or light. Other organic chalcogen compounds include
thioether
In organic chemistry, a sulfide (British English sulphide) or thioether is an organosulfur functional group with the connectivity as shown on right. Like many other sulfur-containing compounds, Volatile organic compound, volatile sulfides have ...
s,
selenoethers and telluroethers. Some of these, such as
dimethyl sulfide
Dimethyl sulfide (DMS) or methylthiomethane is an organosulfur compound with the formula . It is the simplest thioether and has a characteristic disagreeable odor. It is a flammable liquid that boils at . It is a component of the smell produc ...
,
diethyl sulfide, and
dipropyl sulfide are commercially available. Selenoethers are in the form of
R2Se or
RSeR. Telluroethers such as
dimethyl telluride are typically prepared in the same way as thioethers and selenoethers. Organic chalcogen compounds, especially organic sulfur compounds, have the tendency to smell unpleasant. Dimethyl telluride also smells unpleasant, and
selenophenol is renowned for its "metaphysical stench". There are also
thioketones,
selenoketones, and
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.
With metals
There is a very large number of metal chalcogenides. There are also ternary compounds containing
alkali metal
The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...
s and
transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. The lanthanide and actinid ...
s. Highly metal-rich metal chalcogenides, such as
Lu7Te and Lu
8Te have domains of the metal's crystal lattice containing chalcogen atoms. While these compounds do exist, analogous chemicals that contain
lanthanum,
praseodymium,
gadolinium
Gadolinium is a chemical element; it has Symbol (chemistry), symbol Gd and atomic number 64. It is a silvery-white metal when oxidation is removed. Gadolinium is a malleable and ductile rare-earth element. It reacts with atmospheric oxygen or moi ...
,
holmium
Holmium is a chemical element; it has symbol Ho and atomic number 67. It is a rare-earth element and the eleventh member of the lanthanide series. It is a relatively soft, silvery, fairly corrosion-resistant and malleable metal. Like many other ...
,
terbium
Terbium is a chemical element; it has Symbol (chemistry), symbol Tb and atomic number 65. It is a silvery-white, rare earth element, rare earth metal that is malleable and ductile. The ninth member of the lanthanide series, terbium is a fairly ele ...
, or
ytterbium have not been discovered, as of 2008. The
boron group
The boron group are the chemical elements in periodic table group, group 13 of the periodic table, consisting of boron (B), aluminium (Al), gallium (Ga), indium (In), thallium (Tl) and nihonium (Nh). This group lies in the p-block of the perio ...
metals aluminum,
gallium
Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875,
elemental gallium is a soft, silvery metal at standard temperature and pressure. ...
, and
indium
Indium is a chemical element; it has Symbol (chemistry), symbol In and atomic number 49. It is a silvery-white post-transition metal and one of the softest elements. Chemically, indium is similar to gallium and thallium, and its properties are la ...
also form bonds to chalcogens. The Ti
3+ ion forms chalcogenide
dimers such as Ti
Tl5Se
8. Metal chalcogenide dimers also occur as lower tellurides, such as Zr
5Te
6.
Elemental chalcogens react with certain lanthanide compounds to form lanthanide clusters rich in chalcogens.
Uranium
Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...
(IV) chalcogenol compounds also exist. There are also
transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. The lanthanide and actinid ...
chalcogenols which have potential to serve as
catalyst
Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
s and stabilize
nanoparticle
A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At ...
s.
With pnictogens
Compounds with chalcogen-
phosphorus
Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...
bonds have been explored for more than 200 years. These compounds include unsophisticated phosphorus chalcogenides as well as large molecules with biological roles and phosphorus-chalcogen compounds with metal clusters. These compounds have numerous applications, including organo-phosphate insecticides,
strike-anywhere matches and
quantum dot
Quantum dots (QDs) or semiconductor nanocrystals are semiconductor particles a few nanometres in size with optical and electronic properties that differ from those of larger particles via quantum mechanical effects. They are a central topic i ...
s. A total of 130,000 compounds with at least one phosphorus-sulfur bond, 6000 compounds with at least one phosphorus-selenium bond, and 350 compounds with at least one phosphorus-tellurium bond have been discovered. The decrease in the number of chalcogen-phosphorus compounds further down the periodic table is due to diminishing bond strength. Such compounds tend to have at least one phosphorus atom in the center, surrounded by four chalcogens and
side chain
In organic chemistry and biochemistry, a side chain is a substituent, chemical group that is attached to a core part of the molecule called the "main chain" or backbone chain, backbone. The side chain is a hydrocarbon branching element of a mo ...
s. However, some phosphorus-chalcogen compounds also contain hydrogen (such as secondary
phosphine
Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...
chalcogenides) or nitrogen (such as dichalcogenoimidodiphosphates).
Phosphorus selenides are typically harder to handle that phosphorus sulfides, and compounds in the form P
xTe
y have not been discovered. Chalcogens also bond with other
pnictogens
, -
! colspan=2 style="text-align:left;" , ↓ Period (periodic table), Period
, -
! Period 2 element, 2
,
, -
! Period 3 element, 3
,
, -
! Period 4 element, 4
,
, -
! Period 5 element, 5
,
, -
! Period 6 element, 6
,
, -
! Perio ...
, such as
arsenic
Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...
,
antimony
Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient t ...
, and
bismuth
Bismuth is a chemical element; it has symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs nat ...
. Heavier chalcogen pnictides tend to form
ribbon
A ribbon or riband is a thin band of material, typically cloth but also plastic or sometimes metal, used primarily as decorative binding and tying. Cloth ribbons are made of natural materials such as silk, cotton, and jute and of synthetic mate ...
-like polymers instead of individual molecules. Chemical formulas of these compounds include Bi
2S
3 and Sb
2Se
3. Ternary chalcogen pnictides are also known. Examples of these include P
4O
6Se and P
3SbS
3.
salts
In chemistry, a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions ( cations) and negatively charged ions (anions), which results in a compound with no net electric charge (electrically neutral). ...
containing chalcogens and pnictogens also exist. Almost all chalcogen pnictide salts are typically in the form of
xE4x">nxE4xsup>3−, where Pn is a pnictogen and E is a chalcogen. Tertiary phosphines can react with chalcogens to form compounds in the form of R
3PE, where E is a chalcogen. When E is sulfur, these compounds are relatively stable, but they are less so when E is selenium or tellurium. Similarly, secondary phosphines can react with chalcogens to form secondary phosphine chalcogenides. However, these compounds are in a state of
equilibrium with chalcogenophosphinous acid. Secondary phosphine chalcogenides are
weak acids.
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 .
Other
Chalcogens form single bonds and double bonds with other
carbon group
The carbon group is a group (periodic table), periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). It lies within the p-block.
In modern International Union of Pure and Applied Ch ...
elements than carbon, such as
silicon
Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...
,
germanium
Germanium is a chemical element; it has Symbol (chemistry), symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid or a nonmetal in the carbon group that is chemically ...
, 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
hydride
In chemistry, a hydride is formally the anion of hydrogen (H−), a hydrogen ion with two electrons. In modern usage, this is typically only used for ionic bonds, but it is sometimes (and has been more frequently in the past) applied to all che ...
s react or when heavier versions of
carbenes react. Sulfur and tellurium can bond with organic compounds containing both silicon and phosphorus.
All of the chalcogens form
hydride
In chemistry, a hydride is formally the anion of hydrogen (H−), a hydrogen ion with two electrons. In modern usage, this is typically only used for ionic bonds, but it is sometimes (and has been more frequently in the past) applied to all che ...
s. In some cases this occurs with chalcogens bonding with two hydrogen atoms.
However
tellurium hydride and
polonium hydride are both volatile and highly
labile.
Also, oxygen can bond to hydrogen in a 1:1 ratio as in
hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...
, but this compound is unstable.
Chalcogen compounds form a number of
interchalcogens. For instance, sulfur forms the toxic
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...
and
sulfur trioxide
Sulfur trioxide (alternative spelling sulphur trioxide) is the chemical compound with the formula SO3. It has been described as "unquestionably the most conomicallyimportant sulfur oxide". It is prepared on an industrial scale as a precursor to ...
.
Tellurium also forms oxides. There are some chalcogen sulfides as well. These include
selenium sulfide, an ingredient in some
shampoo
Shampoo () is a hair care product, typically in the form of a viscous liquid, that is formulated to be used for cleaning (scalp) hair. Less commonly, it is available in solid bar format. (" Dry shampoo" is a separate product.) Shampoo is use ...
s.
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
Dimethyl sulfide (DMS) or methylthiomethane is an organosulfur compound with the formula . It is the simplest thioether and has a characteristic disagreeable odor. It is a flammable liquid that boils at . It is a component of the smell produc ...
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 Na
2B
2Se
7 contain selenium instead.
History
Early discoveries
Sulfur has been known since
ancient times
Ancient history is a time period from the History of writing, beginning of writing and recorded human history through late antiquity. The span of recorded history is roughly 5,000 years, beginning with the development of Sumerian language, ...
and is mentioned in the Bible fifteen times. It was known to the ancient Greeks and commonly mined by the ancient Romans. In the Middle Ages, it was a key part of alchemy, alchemical experiments. In the 1700s and 1800s, scientists Joseph Louis Gay-Lussac and Louis-Jacques Thénard proved sulfur to be a chemical element.
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. Robert Hooke, Mikhail Lomonosov, Ole Borch, and Pierre Bayden all successfully created oxygen, but did not realize it at the time. Oxygen was discovered by Joseph Priestley in 1774 when he focused sunlight on a sample of 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.
Tellurium was first discovered in 1783 by Franz Joseph Müller von Reichenstein. He discovered tellurium in a sample of what is now known as calaverite. Müller assumed at first that the sample was pure antimony, but tests he ran on the sample did not agree with this. Muller then guessed that the sample was bismuth sulfide, but tests confirmed that the sample was not that. For some years, Muller pondered the problem. Eventually he realized that the sample was gold bonded with an unknown element. In 1796, Müller sent part of the sample to the German chemist Martin Klaproth, who purified the undiscovered element. Klaproth decided to call the element tellurium after the Latin word for earth.
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.
Periodic table placing

Three of the chalcogens (sulfur, selenium, and tellurium) were part of the discovery of Periodic table, periodicity, as they are among a series of triads of elements in the same
group that were noted by Johann Wolfgang Döbereiner as having similar properties.
Around 1865 John Alexander Reina Newlands, 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. His version included a "group b" consisting of oxygen, sulfur, selenium, tellurium, and osmium.
After 1869, Dmitri Mendeleev proposed his periodic table placing oxygen at the top of "group VI" above sulfur, selenium, and tellurium. Chromium, molybdenum, tungsten, and uranium were sometimes included in this group, but they would be later rearranged as part of group 6 element, 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.
Modern discoveries
In the late 19th century, Marie Curie and Pierre Curie discovered that a sample of 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.
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.
Names and etymology
In the 19th century, Jons Jacob Berzelius suggested calling the elements in group 16 "amphigens",
as the elements in the group formed amphid salts (salts of oxyacids, 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.
The name ''chalcogen'' comes from the Greek words ' (, literally "
copper
Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
"), and ' (, born, gender, kindle). It was first used in 1932 by Wilhelm Biltz's group at Leibniz University Hannover, where it was proposed by Werner Fischer (chemist), Werner Fischer.
The word "chalcogen" gained popularity in Germany during the 1930s because the term was analogous to "halogen". 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,
as the vast majority of metal ores are chalcogenides and the word ' in ancient Greek was associated with metals and metal-bearing rock in general; copper, and its alloy
bronze
Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals (such as phosphorus) or metalloid ...
, 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 ' or the Sanskrit word '; 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 ', meaning earth. Polonium is named after Marie Curie's country of birth, Poland.
Livermorium is named for the Lawrence Livermore National Laboratory.
Occurrence
The four lightest chalcogens (oxygen, sulfur, selenium, and tellurium) are all primordial elements on Earth. Sulfur and oxygen occur as constituent copper ores and selenium and tellurium occur in small traces in such ores.
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,
and 65% of the human body.
Oxygen also occurs in many minerals, being found in all oxide minerals and hydroxide minerals, and in numerous other mineral groups.
Stars of at least eight times the mass of the Sun also produce oxygen in their cores via nuclear fusion.
Oxygen is the third-most Abundance of the chemical elements#Universe, abundant element in the universe, making up 1% of the universe by weight.
Sulfur makes up 0.035% of the Earth's crust by weight, making it the 17th most abundant element there
and makes up 0.25% of the human body.
It is a major component of soil. Sulfur makes up 870 parts per million of seawater and about 1 part per billion of the atmosphere.
Sulfur can be found in elemental form or in the form of sulfide minerals, sulfate minerals, or sulfosalt minerals.
Stars of at least 12 times the mass of the Sun produce sulfur in their cores via nuclear fusion.
Sulfur is the tenth most abundant element in the universe, making up 500 parts per million of the universe by weight.
Selenium makes up 0.05 parts per million of the Earth's crust by weight.
This makes it the 67th most Abundance of the chemical elements#Earth, abundant element in the Earth's crust. Selenium makes up on average 5 parts per million of the soils. Seawater contains around 200 parts per trillion of selenium. The atmosphere contains 1 nanogram of selenium per cubic meter. There are mineral groups known as selenate minerals, selenates and selenite minerals, selenites, but there are not many minerals in these groups. Selenium is not produced directly by nuclear fusion.
Selenium makes up 30 parts per billion of the universe by weight.
There are only 5 parts per billion of tellurium in the Earth's crust and 15 parts per billion of tellurium in seawater.
Tellurium is one of the eight or nine least abundant elements in the Earth's crust.
There are a few dozen tellurate minerals and telluride minerals, and tellurium occurs in some minerals with gold, such as sylvanite and calaverite. Tellurium makes up 9 parts per billion of the universe by weight.
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.
The Earth's crust contains less than 1 part per billion of polonium, making it one of the ten rarest metals on Earth.
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
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. Because sulfide minerals are much denser than the silicate minerals formed by lithophile elements,
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.
Production
Approximately 100 million Tonne, 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. 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.

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.
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.
Tellurium is mostly produced as a by-product of the processing of copper. Tellurium can also be refined by 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.
Until the creation of nuclear reactors, all polonium had to be extracted from uranium ore. In modern times, most isotopes of polonium are produced by bombarding
bismuth
Bismuth is a chemical element; it has symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs nat ...
with neutrons.
Polonium can also be produced by high neutron fluxes in nuclear reactors. Approximately 100 grams of polonium are produced yearly.
All the polonium produced for commercial purposes is made in the Ozersk nuclear reactor in Russia. From there, it is taken to Samara, Russia for purification, and from there to St. Petersburg for distribution. The United States is the largest consumer of polonium.
All
livermorium
Livermorium is a synthetic chemical element; it has symbol Lv and atomic number 116. It is an extremely radioactive element that has only been created in a laboratory setting and has not been observed in nature. The element is named after the La ...
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.
Applications
Metabolism is the most important source and use of oxygen. Minor industrial uses include Steelmaking (55% of all purified oxygen produced), the chemical industry (25% of all purified oxygen), medical use, water treatment (as oxygen kills some types of bacteria), rocket fuel (in liquid form), and metal cutting.
Most sulfur produced is transformed into
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...
, which is further transformed into
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
, a very common industrial chemical. Other common uses include being a key ingredient of gunpowder and Greek fire, and being used to change soil pH.
Sulfur is also mixed into rubber to vulcanized rubber, vulcanize it. Sulfur is used in some types of concrete and fireworks. 60% of all sulfuric acid produced is used to generate phosphoric acid.
Sulfur is used as a pesticide (specifically as an acaricide and fungicide) on "orchard, ornamental, vegetable, grain, and other crops."

Around 40% of all selenium produced goes to glassmaking. 30% of all selenium produced goes to metallurgy, including manganese#Occurrence and production, manganese production. 15% of all selenium produced goes to agriculture. Electronics such as photovoltaic, 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.
Tellurium suboxide, a mixture of tellurium and tellurium dioxide, is used in the rewritable data layer of some CD-RW, CD-RW disks and DVD-RW, DVD-RW disks. Bismuth telluride is also used in many microelectronic devices, such as Photodetector, photoreceptors. Tellurium is sometimes used as an alternative to sulfur in vulcanized rubber. Cadmium telluride is used as a high-efficiency material in solar panels.
Some of polonium's applications relate to the element's radioactivity. For instance, polonium is used as an Alpha particle, 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.
Livermorium does not have any uses whatsoever due to its extreme rarity and short half-life.
Organochalcogen compounds are involved in the semiconductor process. These compounds also feature into ligand chemistry and biochemistry. One application of chalcogens themselves is to manipulate redox couples in supramolecular chemistry (chemistry involving non-covalent bond interactions). This application leads on to such applications as crystal packing, assembly of large molecules, and biological recognition of patterns. The secondary bonding interactions of the larger chalcogens, selenium and tellurium, can create organic solvent-holding acetylene non-carbon nanotube, nanotubes. Chalcogen interactions are useful for conformational analysis and stereoelectronic effects, among other things. Chalcogenides with through bonds also have applications. For instance, divalent sulfur can stabilize carbanions,
cation
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
ic centers, and radical (chemistry), radical. Chalcogens can confer upon ligands (such as DCTO) properties such as being able to transform copper, Cu(II) to Cu(I). Studying chalcogen interactions gives access to radical cations, which are used in mainstream synthetic chemistry. Metallic redox centers of biological importance are tunable by interactions of ligands containing chalcogens, such as methionine and
selenocysteine
Selenocysteine (symbol Sec or U, in older publications also as Se-Cys) is the 21st proteinogenic amino acid. Selenoproteins contain selenocysteine residues. Selenocysteine is an analogue of the more common cysteine with selenium in place of the ...
. Also, chalcogen through-bonds can provide insight about the process of electron transfer.
Biological role

Oxygen is needed by almost all life, organisms for the purpose of generating Adenosine triphosphate, 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.
All animals need significant amounts of
sulfur
Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
. 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.
All animals and some plants need trace amounts of
selenium
Selenium is a chemical element; it has symbol (chemistry), symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elem ...
, but only for some specialized enzymes.
Humans consume on average between 6 and 200 micrograms of selenium per day. Mushrooms and brazil nuts are especially noted for their high selenium content. Selenium in foods is most commonly found in the form of amino acids such as
selenocysteine
Selenocysteine (symbol Sec or U, in older publications also as Se-Cys) is the 21st proteinogenic amino acid. Selenoproteins contain selenocysteine residues. Selenocysteine is an analogue of the more common cysteine with selenium in place of the ...
and selenomethionine.
Selenium can protect against heavy metal (chemistry), heavy metal poisoning.
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
dimethyl telluride. Most tellurium in the blood stream is excreted slowly in urine, but some is converted to dimethyl telluride and released through the lungs. On average, humans ingest about 600 micrograms of tellurium daily. Plants can take up some tellurium from the soil. Onions and garlic have been found to contain as much as 300 parts per million of tellurium in dry weight.
Polonium has no biological role, and is highly toxic on account of being radioactive.
Toxicity
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.
Even gaseous oxygen is dangerous in excess. For instance, Underwater diving, sports divers have occasionally drowned from convulsions caused by breathing pure oxygen at a depth of more than underwater.
Oxygen is also toxic to some bacteria.
Ozone, an allotrope of oxygen, is toxic to most life. It can cause lesions in the respiratory tract.
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 (medicine), catharsis
if ingested, and can irritate the mucous membranes. An excess of sulfur can be toxic for Cattle, cows because microbes in the rumens of cows produce toxic hydrogen sulfide upon reaction with sulfur. Many sulfur compounds, such as hydrogen sulfide (H
2S) and
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...
(SO
2) are highly toxic.
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. Hydrogen selenide (H
2Se) is highly toxic.
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.
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 (Na
2TeO
3) is lethal in amounts of around 2 grams.
Polonium is dangerous as an alpha particle emitter. If ingested,
polonium-210
Polonium-210 (210Po, Po-210, historically radium F) is an isotope of polonium. It undergoes alpha decay to stable 206Pb with a half-life of 138.376 days (about months), the longest half-life of all naturally occurring polonium isotopes (210– ...
is a million times as toxic as hydrogen cyanide by weight; it has been used as a murder weapon in the past, most famously Death of Alexander Litvinenko, to kill Alexander Litvinenko.
Polonium poisoning can cause nausea, vomiting, anorexia (symptom), anorexia, and lymphopenia. It can also damage hair follicles and white blood cells.
Polonium-210 is only dangerous if ingested or inhaled because its alpha particle emissions cannot penetrate human skin.
Polonium-209 is also toxic, and can cause leukemia.
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
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
,
sulfur
Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
,
selenium
Selenium is a chemical element; it has symbol (chemistry), symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elem ...
, and
tellurium
Tellurium is a chemical element; it has symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally fou ...
. The term received some use in the early 1800s but is now obsolete.
The current term in use for the 16th group is chalcogens.
See also
* Chalcogenide
* Gold chalcogenides
* Halogen
* Interchalcogen
* Pnictogen
References
External links
*
{{Authority control
Chalcogens,
Periodic table
Groups (periodic table)