Selenium (Se)

Selenium (Se)

Atomic Number: 34
Atomic Weight: 78.96
Melting Point: 217
Boiling Point: 684.9
Specific Gravity: 4.79 (gray) 4.28 (vitreous)
Valence(s): -2, 4 or 6

Berzelius discovered Selenium in 1817. It is found in small quantities in the rare minerals crooksite and clausthalite. Selenium and its compounds are similar to sulphur and its compounds. Photocells are produced from Selenium. Selenium is also used to decolourize glass and photocopy documents. [LM] {RW}