Name Selenium
Symbol Se
Atomic Number 34
Atomic Mass 78.96 atomic mass units
Number of Protons 34
Number of Neutrons 45
Number of Electrons 34
Melting Point 217.0° C
Boiling Point 684.9° C
Density 4.79 grams per cubic centimeter
Normal Phase Solid
Family Nonmetals
Period 4
Costs $300 per pound



Origin of Name From the Greek word selene, meaning moon
Date and Place of Discovery In 1817 in Stockholm, Sweden
Discovered by Jöns Jacob Berzelius
Common Compounds
Interesting facts
  • It is similar to sulfur in its form and compounds.
  • It converts light into electricity.
  • It decreases electrical resistance with increased illumination.
  • It can convert AC electricity to DC electricity.
  • It is found in several forms, but is usually prepared with a crystalline structure.
  • Most forms are non toxic but hydrogen selenide (H2Se) and other selenium compounds are very toxic.
Common Uses
  • Photographic toner
  • Colored glass
  • Enamels decolorize glass
  • Photocells
  • Light meters
  • Rectifiers
  • Solid state electronics (televisions)
  • An additive to stainless steel
  • Herbal health products and vitamins


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