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18Ar39.948
Argon
Noble GasArgon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most common gas in the Earth's atmosphere, at 0.934% (9,340 ppmv), making it over twice as abundant as the next most common atmospheric gas, water vapor (which averages about 4000 ppmv, but varies greatly), and 23 times as abundant as the next most common non-condensing atmospheric gas, carbon dioxide (400 ppmv), and more than 500 times as abundant as the next most common noble gas, neon (18 ppmv).
Phase: GasAppearance: colorless gas exhibiting a lilac/violet glow when placed in a high voltage electric field
2, 8, 8
Physical Properties
Atomic Mass39.9481 u
Density1.784 g/cm³
Melting Point83.81 K
Boiling Point87.302 K
Period3
PhaseGas
Chemical Properties
Electron Configuration1s2 2s2 2p6 3s2 3p6
Semantic Config[Ne] 3s2 3p6
Shells2, 8, 8
Electron Affinity-96 kJ/mol
Ionization Energies
IE1: 1520.6 kJ/molIE2: 2665.8 kJ/molIE3: 3931 kJ/molIE4: 5771 kJ/molIE5: 7238 kJ/molIE6: 8781 kJ/molIE7: 11995 kJ/molIE8: 13842 kJ/molIE9: 40760 kJ/molIE10: 46186 kJ/molIE11: 52002 kJ/molIE12: 59653 kJ/molIE13: 66199 kJ/molIE14: 72918 kJ/molIE15: 82473 kJ/molIE16: 88576 kJ/molIE17: 397605 kJ/molIE18: 427066 kJ/mol
Discovery
Discovered byLord Rayleigh