Actinium

Actinide · 227.02775 u · group 3, period 7

Actinium · Ac

Atomic number89

SymbolAc

CategoryActinide

Standard stateSolid

Group · Period · Block3 · 7 · f

Electron configuration[Rn]7s2 6d1

Atomic mass227.02775 u

Atomic radius260 pm

Protons / Neutrons / Electrons89 / 138 / 89

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

Electronegativity (Pauling)1.1

Ionization energy5.17 eV

Electron affinity—

Oxidation states+3

Melting point1.32e+3 K · 1.05e+3 °C

Boiling point3.47e+3 K · 3.20e+3 °C

Density10.07 g/cm³

Year discovered1899

CPK color

#70ABFA

State at room temp (25 °C)

solid

Position