Argon

Argon
	18Ar
	chlorine ← argon → potassium
Panagway
	colorless gas exhibiting a lilac/violet glow when placed in a high voltage electric field; ; ; Spectral lines of argon
Kinatibuk-ang mga kinaiya
Ngalan, simbolo, kaiphan	argon, Ar, 18
Paglitok	/ˈɑːrɡɒn/
Kategoriyang elemento	gas nga halangdon
Group, period, block	18, 3, p
Gibug-aton sa atomo	39.948(1)
Kontorno sa elektron	[Ne] 3s2 3p6; 2, 8, 8 Electron shells of argon (2, 8, 8)
History
Pagkadiskobre	Lord Rayleigh and William Ramsay (1894)
First isolation	Lord Rayleigh and William Ramsay (1894)
Physical properties
Phase	gas
Density	(0 °C, 101.325 kPa); 1.784 g/L
Liquid density at b.p.	1.40 g·cm−3
Melting point	83.80 K, −189.35 °C, −308.83 °F
Boiling point	87.30 K, −185.85 °C, −302.53 °F
Triple point	83.8058 K (-189°C), 69 kPa
Critical point	150.87 K, 4.898 MPa
Heat of fusion	1.18 kJ·mol−1
Heat of vaporization	6.43 kJ·mol−1
Molar heat capacity	5R/2 = 20.786 J·mol−1·K−1
Vapor pressure
Atomic properties
Oxidation states	0
Electronegativity	no data (Pauling scale)
Ionization energies; (more)	1st: 1520.6 kJ·mol−1
	2nd: 2665.8 kJ·mol−1
	3rd: 3931 kJ·mol−1
Covalent radius	106±10 pm
Van der Waals radius	188 pm
Miscellanea
Crystal structure	face-centered cubic
Magnetic ordering	diamagnetic
Thermal conductivity	17.72x10-3 W·m−1·K−1
Speed of sound	(gas, 27 °C) 323 m·s−1
CAS registry number	7440–37–1
Most stable isotopes
	Main article: Isotopes of argon
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