Name Promethium
Symbol Pm
Atomic Number 61
Atomic Mass 145.0 atomic mass units
Number of Protons 61
Number of Neutrons 84
Number of Electrons 61
Melting Point 1042.0 C
Boiling Point 3000.0 C
Density 6.475 grams per cubic centimeter
Normal Phase Synthetic
Family Rare Earth Metals
Period 6
Cost 50 cents per curie



Origin of Name After the Greek god, Prometheus, who stole fire from the sky and gave it to man
Date and Place of Discovery In 1944 at the Clinton Laboratories in Oak Ridge, Tennessee as part of the Manhattan Project, but not documented or claimed until 1946
Discovered by Jacob A. Marinsky, Lawrence E. Glendenin and Charles D. Coryell
Common Compounds
Interesting facts
  • Its existence was predicted by Bohuslav Brauner in 1902, which was supported by Henry Moseley in 1914
  • It was discovered while analyzing the byproducts of uranium fission in a nuclear reactor.
  • Only trace amounts have been found in nature.
  • It has been found in pitchblende.
  • It is highly radioactive.
  • It can generate X-rays during beta decay.
Common Uses
  • Thickness gauges.
  • Nuclear batteries
  • Luminous paint for watches
  • Luminous paints
  • Possible future uses: X-rays, space probes and satellites


Chemical Elements
Jefferson Lab
Web Elements

Promethium Atomic Structure Elements by Name Elements by Number Home