Chalcogen

The chalcogens (pronunciation: ˈkal-kə-jəns) are the chemical elements in group 16 (old-style: VIB or VIA) of the periodic table. This group is also known as the oxygen family. It consists of the elements oxygen (O), sulphur (S), selenium (Se), tellurium (Te), the radioactive element polonium (Po), and the synthetic element ununhexium (Uuh).

The name means "ore former" from the Greek chalcos = ore and -gen = formation.
Although all group 16 elements of the periodic table are defined as chalcogens, the term is more commonly reserved for sulfides, selenides, and tellurides, rather than oxides. The compounds of the heavier chalcogens (particularly the sulfides, selenides, and tellurides) are collectively known as chalcogenides.^[1] Oxides from a lighter chalcogen, are usually not indicated as chalcogenides.

Properties

Members of this group show similar patterns in their electron configuration, especially the outermost shells, resulting in similar trends in chemical behavior:

Oxygen and sulfur are nonmetals, and polonium, selenium, and tellurium are metalloid semiconductors (that means, their electrical properties are between those of a metal and an insulator). Nevertheless, tellurium, as well as selenium, is often referred to as a metal when in elemental form.

Metal chalcogenides are common as minerals. For example, pyrite (FeS₂) is an iron ore. The rare mineral calaverite is the ditelluride AuTe₂.

The formal oxidation number of the most common chalcogen copounds is −2. Other values, such as −1 in pyrite, can be attained. The highest formal oxidation number +6 is found in sulfates, selenates and tellurates, such as in sulphuric acid or sodium selenate (Na₂SeO₄).

See also

• Gold chalcogenides

References