* Selenium is a member of the main group nonmetals family:
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SELENIUM / Se / 34
Selenium occurs as a silvery metal or red powder, the powder
being derived by heating the metal. It has moderate
resistance to corrosion. Six isotopes are found in nature:
Se<80/34> / 50%
Se<79/34> / 23.5%
Se<76/34> / 9%
Se<82/34> / 9%
Se<77/34> / 7%
Se<74/34> / 1%.
All are stable. Radioactive Se<75/34>, with a half-life of 13
weeks, is sometimes used as a tracer.
atomic weight: 78.96
abundance: 67th
density: 4.79 gm/cc
melting point: 217 C
boiling point: 685 C
valence: -2 <4> 6
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Selenium is the least economically important of the nonmetals, with production of only a few thousand tonnes a year. It has modest uses in photoelectric cells and "cadmium selenide (CdSe)" infrared detectors, as well as glassmaking.
