Periodic Table
18
Ar
39.948
Argon
Noble GasMost abundant noble gas in air (~0.93%); used as inert atmosphere.
Electronic Configuration
[Ne] 3s² 3p⁶or1s² 2s² 2p⁶ 3s² 3p⁶
Electron shells
2e⁻n=1
8e⁻n=2
8e⁻n=3
Properties
Atomic number
18
Atomic mass
39.948 u
Category
Noble Gas
Block / Group / Period
p · 18 · 3
Valence electrons
8
Oxidation states
0
Electronegativity
—
Atomic radius
71 pm
Ionization energy
1521 kJ/mol
Electron affinity
0 kJ/mol
Melting point
84 K / -189 °C
Boiling point
87 K / -186 °C
Density
0.001784 g/cm³
State at 25 °C
gas
Personal Notes
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