Periodic Table of Elements




Promethium was first produced at Oak Ridge National Laboratory in 1945 by Jacob A. Marinsky, Lawrence E. Glendenin and Charles D. Coryell by separation and analysis of the fission products of uranium fuel irradiated in the graphite reactor. But its discovery was announced in 1947.

Name: Promethium
Atomic number: 61
Atomic weight: 144.91
State: solid
Group, period, block: n/a, 6, f
Color: metallic
Classification: lanthanide
Electron configuration: 6s2 4r5

Physical properties

Density: 7.26 g/cm-3
Melting point: 1315 K,1042 C,1908 F
Boiling point: 3273 K,3000 C,5432 F

Atomic properties

Oxidation states: 3
Electronegativity: 1.13 (Pauling scale)
Ionization energies: 1st: 540 kJmol-1
Covalent radius: 199 pm
Van der Waals radius: no data
  • Pm
  • Electron Configuration


Promethium has no stable isotopes, and does not exist in nature, except in trace quantities as a product of spontaneous fission and alpha decay of 151Eu.