Template:Infobox argon

Argon,  ₁₈Ar

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General properties
Pronunciation	Template:Infobox element/pronunciation
Appearance	colorless gas exhibiting a lilac/violet glow when placed in an electric field
Standard atomic weight (Ar, standard)	Template:Infobox element/standard atomic weight
Mass number	Template:Infobox element/symbol-to-most-stable-isotope (most stable isotope)
Argon in the periodic table
Template:Infobox element/periodic table
Atomic number (Z)	18
Group	Template:Infobox element/group
Period	period 3
Block	p-block
Element category	Template:Infobox element/category format
Electron configuration	[Ne] 3s2 3p6
Electrons per shell	2, 8, 8
Physical properties
Phase at STP	gas
Melting point	83.81 K ​(−189.34 °C, ​−308.81 °F)
Boiling point	87.302 K ​(−185.848 °C, ​−302.526 °F)
Density (at STP)	1.784 g/L
when liquid (at b.p.)	1.3954 g/cm3
Triple point	83.8058 K, ​68.89 kPa
Critical point	150.687 K, 4.863 MPa
Heat of fusion	1.18 kJ/mol
[[Enthalpy of vaporization|Heat of Template:Engvar]]	6.53 kJ/mol
Molar heat capacity	20.85 J/(mol·K)
[[Vapor pressure|Template:Engvar pressure]] Template:Infobox element/vapor pressure table
Atomic properties
Oxidation states	Template:Infobox element/symbol-to-oxidation-state
Electronegativity	Pauling scale: no data
[[Ionization energy|Template:Engvar energies]]	1st: 1520.6 kJ/mol 2nd: 2665.8 kJ/mol 3rd: 3931 kJ/mol (more)
Covalent radius	106±10 pm
Van der Waals radius	188 pm
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Other properties
Crystal structure	​Template:Infobox element/crystal structure Template:Infobox element/crystal structure
Speed of sound	323 m/s (gas, at 27 °C)
Thermal conductivity	17.72Template:E  W/(m·K)
Magnetic ordering	diamagnetic
Magnetic susceptibility	−19.6·10−6 cm3/mol
CAS Number	7440-37-1
History
Discovery and first isolation	Lord Rayleigh and William Ramsay (1894)
Main isotopes of argon
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Template:Infobox element/element navigation Template:Template reference list Two of these are named references. They may be cited in the containing article as

• <ref name="CIAAW2016" /> for the source Atomic weights of the elements 2013 (from subtemplates used by {{Infobox element}})
• <ref name="b92" /> for the source edited by Haynes