91 – Pa – Protactinium

Pa-231 (half life 32700 years) is part of the decay chain of U-235, so traces of Protactinium exist in the pitchblende shown here. Amount: 0.2 g pitchblende, corresponding to 37 ng or 100 trillion atoms of Pa-231.

Physical and chemical data
Atomic mass	231.03588
Density	15.37 g·cm^-3
Melting point	1572 °C
Boiling point	4227 °C
Abundance	9.00e-11 %
Electronegativy	1.1
Oxydation levels	[5], 4
Electron configuration	[Rn]5f2 6d 7s2