Argon

chlorine – argon Ne Ar Kr       Full table
General
Name, Symbol, Number	argon, Ar, 18
Chemical series	noble gases
Group, Period, Block	18 (VIIIA), 3 , p
Density, Hardness	1.784 kg/m3 (273 K), NA
Appearance	Colorless
Atomic properties
Atomic weight	39.948 amu
Atomic radius (calc.)	no data (71 pm)
Covalent radius	97 pm
van der Waals radius	188 pm
Electron configuration	[Ne]3s2 3p6
e- 's per energy level	2, 8, 8
Oxidation states (Oxide)	0 (unknown)
Crystal structure	cubic face centered
Physical properties
State of matter	gas (nonmagnetic)
Melting point	83.8 K (−308.7 °F)
Boiling point	87.3 K (−302.4 °F)
Molar volume	22.56 ×10−6 m3/mol
Heat of vaporization	6.447 kJ/mol
Heat of fusion	1.188 kJ/mol
Vapor pressure	NA
Speed of sound	319 m/s at 293.15 K
Miscellaneous
Electronegativity	no data (Pauling scale)
Specific heat capacity	520 J/(kg*K)
Electrical conductivity	no data
Thermal conductivity	0.01772 W/(m*K)
1st ionization potential	1520.6 kJ/mol
2nd ionization potential	2665.8 kJ/mol
3rd ionization potential	3931 kJ/mol
4th ionization potential	5771 kJ/mol
5th ionization potential	7238 kJ/mol
6th ionization potential	8781 kJ/mol
7th ionization potential	11995 kJ/mol
8th ionization potential	13842 kJ/mol
Most stable isotopes
iso NA half-life DM DE MeV DP 36Ar 0.336% Ar is stable with 18 neutrons 38Ar 0.063% Ar is stable with 20 neutrons 39Ar {syn.} 269 y β- 0.565 39K 40Ar 99.6% Ar is stable with 22 neutrons 42Ar {syn} 32.9 y β- 0.600 42K
SI units & STP are used except where noted.

Argon is a chemical element. The symbol for argon is Ar, and its atomic number (or proton number) is 18. It is a noble gas and no electrons or protons can be lost or gained from this atom.

Argon atoms are found in air. About 1% of the Earth's atmosphere (the air around us) is argon.

Other pages

• List of common elements
• Periodic table