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Group → 16
↓ Period
2 8
O
3 16
S
4 34
Se
5 52
Te
6 84
Po
7 116
Uuh

The chalcogens (pronounced /ˈkæl kə dʒən/) 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), sulfur (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, including oxygen are defined as chalcogens, oxygen and oxides are usually distinguished from chalcogens and chalcogenides. The term chalcogenide is more commonly reserved for sulfides, selenides, and tellurides, rather than for oxides. Oxides are usually not indicated as chalcogenides. [1] [2] [3] [4]

Properties

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

Z Element No. of electrons/shell
8 oxygen 2, 6
16 sulfur 2, 8, 6
34 selenium 2, 8, 18, 6
52 tellurium 2, 8, 18, 18, 6
84 polonium 2, 8, 18, 32, 18, 6
116 ununhexium 2, 8, 18, 32, 32, 18, 6

Oxygen and sulfur are nonmetals, and selenium, tellurium, and polonium 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 sulfuric acid or sodium selenate (Na2SeO4).

Explanation of above periodic table slice:
Nonmetals Metalloids Poor metals Atomic numbers in red are gases Atomic numbers in black are solids Solid borders indicate primordial elements (older than the Earth) Dashed borders indicate radioactive natural elements Dotted borders indicate radioactive synthetic elements

See also

References

  1. ^ A Second Note on the Term "Chalcogen"
  2. ^ Francesco Devillanova (Editor) Handbook of Chalcogen Chemistry - New Perspectives in Sulfur, Selenium and Tellurium Royal Society of Chemistry, 2007; ISBN 0854043667, 9780854043668
  3. ^ IUPAC goldbook amides. Chalcogen replacement analogues (of amides) are called thio-, seleno- and telluro-amides.
  4. ^ Ohno Takahisa Passivation of GaAs(001) surfaces by chalcogen atoms (S, Se and Te) Surface Science; Volume 255, Issue 3, 2 September 1991, Pages 229-236; doi:10.1016/0039-6028(91)90679-M
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