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34 Se

Selenium

Nonmetal
Atomic Mass
78.971 u
Density
4.82 g/cm³ (gray)
Melting Point
221 °C (gray)
Boiling Point
685 °C
State
Solid
Discovery
1817

Discovery

Discovered by Jöns Jacob Berzelius and Johann Gottlieb Gahn in 1817.

Common Uses

  • Photovoltaic cells and solar panels
  • Used in photocopiers and laser printers
  • Used to decolorize glass and to make red-colored glass
  • Dietary supplement for animals and humans

Interesting Facts

  • Named after the Greek word for the moon, "selene".
  • Its electrical conductivity increases when exposed to light (photoconductivity).
  • Exists in several allotropic forms, including red, black, and gray (metallic) selenium.
  • An essential trace element for many organisms, but can be toxic in high doses.
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