Promethium

Lanthanide · 144.91276 u · group 3, period 6

Promethium · Pm

Atomic number61

SymbolPm

CategoryLanthanide

Standard stateSolid

Group · Period · Block3 · 6 · f

Electron configuration[Xe]6s2 4f5

Atomic mass144.91276 u

Atomic radius236 pm

Protons / Neutrons / Electrons61 / 84 / 61

Shells (e⁻ per shell)2, 8, 18, 23, 8, 2

Electronegativity (Pauling)—

Ionization energy5.55 eV

Electron affinity—

Oxidation states+3

Melting point1.32e+3 K · 1.04e+3 °C

Boiling point3.27e+3 K · 3.00e+3 °C

Density7.26 g/cm³

Year discovered1945

CPK color

#A3FFC7

State at room temp (25 °C)

solid

Position