Argon

Argon, ₀₀Ar

Argon
Pronunciation	/ˈɑːrɡɒn/ ​(AR-gon)
Appearance	colorless gas exhibiting a lilac/violet glow when placed in an electric field
Standard atomic weight Ar°(Ar)
	[39.792, 39.963][1]
Argon in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Ne ↑ Ar ↓ Kr chlorine ← argon → potassium
Group	group 18 (noble gases)
Period	period 3
Block	p-block
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[2]
Critical point	150.687 K, 4.863 MPa[2]
Heat of fusion	1.18 kJ/mol
Heat of vaporization	6.53 kJ/mol
Molar heat capacity	20.85[3] J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K)   47 53 61 71 87
Atomic properties
Oxidation states	0
Electronegativity	Pauling scale: no data
Ionization 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
Spectral lines of argon
Other properties
Natural occurrence	primordial
Crystal structure	​face-centered cubic (fcc)
Speed of sound	323 m/s (gas, at 27 °C)
Thermal conductivity	17.72×10−3  W/(m⋅K)
Magnetic ordering	diamagnetic[4]
Molar magnetic susceptibility	−19.6·10−6 cm3/mol[5]
CAS Number	7440-37-1
History
Discovery and first isolation	Lord Rayleigh and William Ramsay (1894)
Isotopes of argon v e
Main isotopes[6] Decay abun­dance half-life (t1/2) mode pro­duct 36Ar 0.334% stable 37Ar synth 35 d ε 37Cl 38Ar 0.0630% stable 39Ar trace 268 y β− 39K 40Ar 99.6% stable 41Ar synth 109.34 min β− 41K 42Ar synth 32.9 y β− 42K
Category: Argon view talk edit | references

Argon is a chemical element. Its symbol is argon is Ar and its atomic number is 18. It is part of the noble gas group. It is an odorless and tasteless gas. Argon is the third-most abundant gas in the Earth's atmosphere.

The name "argon" is from the Greek word ἀργός meaning "lazy" or "inactive" because it does not react with other chemicals.

1. ↑ "Standard Atomic Weights: Argon". CIAAW. 2017.
2. ↑ ^{2.0 2.1} Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.121. ISBN 1439855110.
3. ↑ Shuen-Chen Hwang, Robert D. Lein, Daniel A. Morgan (2005). "Noble Gases". Kirk Othmer Encyclopedia of Chemical Technology. Wiley. pp. 343–383. doi:10.1002/0471238961.0701190508230114.a01.
4. ↑ Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
5. ↑ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
6. ↑ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.