Name Thorium
Symbol Th
Atomic Number 90
Atomic Mass 232.038 atomic mass units
Number of Protons 90
Number of Neutrons 142
Number of Electrons 90
Melting Point 1750.0° C
Boiling Point 4790.0° C
Density 11.72 grams per cubic centimeter
Normal Phase Solid
Family Rare Earth Metals
Period Number 6
Cost $150 per ounce



Origin of Name After Thor, the Scandinavian god of thunder
Date and Place of Discovery In 1828 in Sweden
Discovered by Jöns Jacob Berzelius
Common Compounds
Interesting facts
  • It is not highly radioactive.
  • It is found in small amounts in rocks and soils.
  • It is about three times more abundant than uranium and about as common as lead.
  • About 25% of the world's thorium is found in India.
  • It is a silvery white metal which maintains its luster for several months unless it is exposed to oxygen and then it eventually turns black.
  • It decays very slowly.
  • It is being considered as an alternate nuclear fuel to uranium.
Common Uses
  • An alloy element with magnesium
  • A coating of tungsten wire in electronic equipment
  • Tungsten arc welding
  • Heat-resistant ceramics
  • Fuel cycles in nuclear reactors
  • Radiation shields
  • Mantles in gas lights
  • Crucibles
  • Glasses with a high refractive index and low dispersion
  • Lenses for cameras and scientific instruments
  • Catalysts
  • X-ray diagnostics


Photo Courtesy of
Chemical Elements
Jefferson Labs
Web Elements

Thorium Atomic Structure Elements by Name Elements by Number