Chalcogen
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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 are the chemical elements in group 16 (old-style: VIB or VIA) of the periodic table. This group is sometimes 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).
Like other groups, members of this family 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 |
The compounds of the heavier chalcogens (particularly the sulfides, selenides, and tellurides) are collectively known as chalcogenides. Unless grouped with a heavier chalcogen, oxides are not considered chalcogenides.[1] The name is generally considered to mean "ore former" from the Greek chalcos "ore" and -gen "formation".[2]
Oxygen and sulfur are nonmetals, and polonium, selenium and tellurium are metalloid semiconductors (i.e., 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.
Chalcogens are common as minerals. For example, pyrite (FeS2) is an iron ore, and the gold rush town Telluride, Colorado derives its name from the telluride calaverite (AuTe2).
The formal oxidation number of the chalcogens is generally −2 in a chalcogenide but 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). Modern chemical understanding based on quantum theory supersedes the use of formal oxidation numbers in favour of a many-electron wavefunction approach allowing detailed computer simulation. The former concept, while flawed, is still useful in thought experiments and teaching redox reactions.
| 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 |
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[edit] See also
[edit] External links
- ^ US patent application 2007092648, , "Chalcogenide solar cells", published 2007-04-26 , assigned to Nanosolar, Inc.
- ^ A Second Note on the Term "Chalcogen"
