Atomic symbol - Pm
Atomic weight - (144.9127)
Atomic number - 61
Electron configuration - 2-8-18-23-8-2
Oxidation states - +3
State of matter - synthetic
Heavy metal-brittle
Discovered in 1947 by J.A. Marinsky, L.E. Glendenin, and C.D. Coryell
Boils at 2460 .C, melts at 1080 .C

Notes:
Promethium was the last of the rare-earth metals to be discovered. Its soft
beta radiation can be coverted into electricity by sandwiching promethium and
semiconductors such as silicon together; these "batteries" can last as long as
5 years in extreme temperatures.