Atomic number: 61

Symbol: Pm

Category: lanthanoid metal

Density at 25°C: solid: density: 7.26 g·cm−3  [7.220] 

All forms of promethium are radioactive. This partly explains why it was hard to discover initially and in fact wasn't produced until about 1945 in a laboratory in the US. 

Use, natural applications or common combinations: 

  • specialised batteries
  • some long lasting glowing paints
  • used for measuring thicknesses of materials

Basic characteristics:

  • Standard atomic weight: [144.913] varies
  • Melting point:  1042 °C 
  • Boiling point: 3000 °C
  • Radioactivity: all radioactive.
  • 145Pm half life of 17.7 years decays via electron capture ( usually releases a gamma ray)
  • 147Pm half life 2.63 years beta- decay (electrons released) meaning less hazardous. some x-rays released.