Name :  Promethium
Symbol :  Pm
Atomic Number :  61
Atomic Weight :  -144.9127
Specific Heat :  0.18 J/gK
Melting Point :  1042°C
Vaporization :  -
Boiling Point :  3000 °C (estimated)
Electronegativity :  1.13
Density@293 K :  6.475 g/cm³
Discovered :  J.A. Marinsky, L.E. Glendenin, C.D. Coryell, United States, 1945
Description :  Rare earth metal of synthetic origin on the earth, naturally made in stars.
Uses :  It has been used as a source of radioactivity for thickness-measuring gages.