Argon

Noble gas · 39.9 u · group 18, period 3

Argon · Ar

Atomic number18

SymbolAr

CategoryNoble gas

Standard stateGas

Group · Period · Block18 · 3 · p

Electron configuration[Ne]3s2 3p6

Atomic mass39.9 u

Atomic radius188 pm

Protons / Neutrons / Electrons18 / 22 / 18

Shells (e⁻ per shell)2, 8, 8

Electronegativity (Pauling)—

Ionization energy15.76 eV

Electron affinity—

Oxidation states0

Melting point83.8 K · -189.3 °C

Boiling point87.3 K · -185.8 °C

Density0.0018 g/cm³

Year discovered1894

CPK color

#80D1E3

State at room temp (25 °C)

gas

Position