NO. 091Actinide

Pa

Protactinium

Protactinium is a rare, dense, and radioactive actinide. It has no significant commercial uses and is primarily of interest in nuclear research.

Crystal Structure

Face-centered cubic

Atomic Mass231.04 u

Density15.4 g/cm³

Melting Point1841 K

Boiling Point4300 K

Atomic Radius161 pm

Electronegativity1.5

Ionization Energy568 kJ/mol

Electron Affinity50 kJ/mol

Bonding TypeMetallic

Oxidation States4, 5

Acid/BaseBasic

ReactivityHigh

Electron Configuration

[Rn] 5f2 6d1 7s2

Discovered ByKasimir Fajans

Year1913

Known Isotopes

Pa-231