The

chalcogen The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. 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 radioa ...

s react with each other to form interchalcogen compounds. Although no chalcogen is extremely

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 ...

,This article uses Pauling

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 ...

throughout. nor quite as

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 ...

as the halogen fluorine (the most electronegative element), there is a large difference in electronegativity between the top (

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

= 3.44 — the second most electronegative element after fluorine) and bottom (

polonium Polonium is a chemical element with the symbol Po and atomic number 84. Polonium is a chalcogen. A rare and highly radioactive metal with no stable isotopes, polonium is chemically similar to selenium and tellurium, though its metallic characte ...

= 2.0) of the group. Combined with the fact that there is a significant trend towards increasing metallic behaviour while descending the group (oxygen is a gaseous

nonmetal In chemistry, a nonmetal is a chemical element that generally lacks a predominance of metallic properties; they range from colorless gases (like hydrogen) to shiny solids (like carbon, as graphite). The electrons in nonmetals behave differen ...

, while polonium is a silvery

post-transition metal The metallic elements in the periodic table located between the transition metals and the chemically weak nonmetallic metalloids have received many names in the literature, such as ''post-transition metals'', ''poor metals'', ''other metals'', ...

The classification of

as a

or a metalloid is disputed.), this causes the interchalcogens to display many different kinds of bonding:

covalent 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 ...

, ionic, metallic, and

semimetal A semimetal is a material with a very small overlap between the bottom of the conduction band and the top of the valence band. According to electronic band theory, solids can be classified as insulators, semiconductors, semimetals, or metal ...

lic.The heavier halogens are sufficiently electronegative to prevent ionic or metallic bonding in the interhalogens, and the lighter

pnictogen A pnictogen ( or ; from grc, πνῑ́γω "to choke" and -gen, "generator") is any of the chemical elements in group 15 of the periodic table. Group 15 is also known as the nitrogen group or nitrogen family. Group 15 consists of the el ...

s are not sufficiently electronegative to allow ionic or metallic bonding in the interpnictogens.

Known binary interchalcogens

Bonding in the binary interchalcogens

Going down the above table, there is a transition from covalent bonding (with discrete

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bio ...

s) to

ionic bond Ionic bonding is a type of chemical bonding that involves the electrostatic attraction between oppositely charged ions, or between two atoms with sharply different electronegativities, and is the primary interaction occurring in ionic compoun ...

ing; going across the table, there is a transition from

ing to

metallic bond Metallic bonding is a type of chemical bonding that arises from the electrostatic attractive force between conduction electrons (in the form of an electron cloud of delocalized electrons) and positively charged metal ions. It may be descr ...

ing. (Covalent bonding occurs when both elements have similar high electronegativities; ionic bonding occurs when the two elements have very different electronegativities, one low and the other high; metallic bonding occurs when both elements have similar low electronegativities.) For example, in the leftmost column of the table (with bonds to oxygen), O₂ and O₃ are purely covalent, SO₂ and SO₃ are polar molecules, SeO₂ forms chained

polymer A polymer (; Greek ''poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and ...

s (stretching in one dimension), TeO₂ forms layered polymers (stretching in two dimensions), and PoO₂ is ionic with the

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs sca ...

structure (spatial polymers, stretching in three dimensions); in the bottom row of the table (with bonds to polonium), PoO₂ and PoS are ionic, Po_''x''Se_''y'' and Po_''x''Te_''y'' are semimetallic, and Po_∞ is metallic.

Summary of known binary interchalcogens

Sulfur chalcogenides

Lower sulfur oxides The lower sulfur oxides are a group of inorganic compounds with the formula SmOn, where 2m > n. These species are often unstable and thus rarely encountered in everyday life. They are significant intermediates in the combustion of elemental su ...

, S_xO_y where the ratio X:Y is greater than 1:2 **

Disulfur monoxide Disulfur monoxide or sulfur suboxide is an inorganic compound with formula S2O, one of the lower sulfur oxides. It is a colourless gas and condenses to give a roughly dark red coloured solid that is unstable at room temperature. occurs rarely in ...

, S₂O **

Disulfur dioxide Disulfur dioxide, dimeric sulfur monoxide or SO dimer is an oxide of sulfur with the formula S2O2. The solid is unstable with a lifetime of a few seconds at room temperature. Structure Disulfur dioxide adopts a ''cis'' planar structure with ''C'' ...

, S₂O₂ **

Sulfur monoxide Sulfur monoxide is an inorganic compound with formula . It is only found as a dilute gas phase. When concentrated or condensed, it converts to S2O2 ( disulfur dioxide). It has been detected in space but is rarely encountered intact otherwise. S ...

, SO *

Sulfur dioxide Sulfur dioxide ( IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic ...

, SO₂ * Sulfur trioxide, SO₃ *

Higher sulfur oxides Higher sulfur oxides are a group of chemical compounds with the formula SO3+x where x lies between 0 and 1. They contain peroxo (O−O) groups, and the oxidation state of sulfur is +6 as in SO3. Monomeric SO4 can be isolated at low temperatures ...

, SO_x where x>3

Selenium chalcogenides

* Selenium dioxide, SeO₂ * Selenium trioxide, SeO₃ *Many "alloys" of

selenium Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and telluriu ...

and

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...

in different concentrations with semimetallic bonding, Se_''x''S_''y'' **" Selenium monosulfide", SeS **" Selenium disulfide", SeS₂, actually a 2:1 mixture of cyclo-Se₃S₅ and cyclo-Se₂S₆ **" Selenium trisulfide", SeS₃, actually occurring as the cyclic dimer Se₂S₆

Tellurium chalcogenides

* Tellurium monoxide, TeO (unstable transient species) * Tellurium dioxide, TeO₂ * Tellurium trioxide, TeO₃ * Ditellurium pentoxide, Te₂O₅ *Many "alloys" of

tellurium Tellurium is a chemical element with the 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 fo ...

and

in different concentrations with semimetallic bonding, Te_''x''S_''y'' *Many "alloys" of

and

in different concentrations with semimetallic bonding, Te_''x''Se_''y''

Polonium chalcogenides

* Polonium monoxide, PoO * Polonium dioxide, PoO₂ *

Polonium trioxide Polonium trioxide (also known as polonium(VI) oxide) is a chemical compound with the formula Po O3. It is one of three oxides of polonium, the other two being polonium monoxide (PoO) and polonium dioxide (PoO2). It is an interchalcogen. It has ...

, PoO₃ * Polonium monosulfide, PoS *Many "alloys" of

and

in different concentrations with semimetallic bonding, Po_''x''Se_''y'' *Many "alloys" of

and

in different concentrations with semimetallic bonding, Po_''x''Te_''y''

Notes

References

{{reflist * Chalcogens