Protactinium (Pa)

Protactinium (Pa)

Atomic Number: 91
Atomic Weight: 231.04
Melting Point: <1600
Boiling Point: not known
Specific Gravity: 15.37
Valences: 4 or 5

Protactinium was discovered in 1917 by 3 independent teams of scientists. It is a radioactive metal that is one of the rarest, most expensive elements. It can be found in uranium ores. Some protactinium compounds are coloured, and both the element and its compounds are toxic. [LM] {RW}