Name Osmium
Symbol Os
Atomic Number 76
Atomic Mass 190.23 atomic mass units
Number of Protons 76
Number of Neutrons 114
Number of Electrons 76
Melting Point 3045.0° C
Boiling Point 5027.0° C
Density 22.4 grams per cubic centimeter
Normal Phase Solid
Family Transition Metals
Period 6
Cost $100 per gram



Origin of Name From the Greek word osmė, meaning odor
Date and Place of Discovery In 1803 in England
Discovered by Smithson Tennant
Common Compounds
Interesting facts
  • It does not oxidize easily in air unless it is heated.
  • When heated it forms osmium tetroxide, which is very toxic.
  • It is not affected by most acids.
  • It is found in platinum ores and in a mineral called osmiridium, which is very rare.
  • It is also a byproduct of refining nickel ores mined in the Sudbury Basin, Ontario, Canada.
  • It has the highest melting point and the lowest vapor pressure of the platinum elements.
Common Uses
  • Microscopy fingerprint detection
  • Catalyst
  • Fountain pen points
  • Phonographic needles
  • Instrument bearings
  • Electrical light filaments
  • Hard alloys


Photo Courtesy of About.com
Chemical Elements
Mrs. Purdy's Web Page
Web Elements

Osmium Atomic Structure Elements by Name Elements by Number