Promethium (formerly prometheum) is a chemical element with symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms, a distinction shared with technetium.

Atomic Weight:  523
Density:        23.67 g/cm3
Melting Point:  233 °C
 Boiling Point: 2343°C