Protactinium

Actinide · 231.03588 u · group 3, period 7

Protactinium · Pa

Atomic number91

SymbolPa

CategoryActinide

Standard stateSolid

Group · Period · Block3 · 7 · f

Electron configuration[Rn]7s2 5f2 6d1

Atomic mass231.03588 u

Atomic radius243 pm

Protons / Neutrons / Electrons91 / 140 / 91

Shells (e⁻ per shell)2, 8, 18, 32, 20, 9, 2

Electronegativity (Pauling)1.5

Ionization energy5.89 eV

Electron affinity—

Oxidation states+5, +4

Melting point1.85e+3 K · 1.57e+3 °C

Boiling point—

Density15.37 g/cm³

Year discovered1913

CPK color

#00A1FF

State at room temp (25 °C)

solid

Position