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Atomic Number	18

Atomic Symbol	Ar

Atomic Weight	39.948 amu

Group	Noble Gas, 18

Form	Gas

Density @ STP	1.756 g/L

Melting Point	-189.35 °C (-308.83 °F, 83.8 °K)

Boiling Point	-185.85°C (-302.53 °F, 87.3 °K)

Heat of Fusion	1.12 kJ/mol

Heat of Vaporization	6.43 kJ/mol

First Ionization Potential	15.75962 eV

Specific Heat Capacity	0.520 J/g K

Ground State Electron Configuration	3p⁶

Oxidation State(s)	0

Stable Isotopes and Natural Abundance on Earth	³⁶Ar, 0.337%; ³⁸Ar, 0.063%; ⁴⁰Ar, 99.600%

Atomic Radius	71 pm

Crystal Structure	Cubic

Discovered by	Ramsay; Rayleigh, 1894