Argon, 18Ar
Vial containing a violet glowing gas
Argon
Pronunciation/ˈɑːrɡɒn/ (AR-gon)
Appearancecolorless gas exhibiting a lilac/violet glow when placed in an electric field
Standard atomic weight Ar°(Ar)
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
chlorineargonpotassium
Atomic number (Z)18
Groupgroup 18 (noble gases)
Periodperiod 3
Block  p-block
Electron configuration[Ne] 3s2 3p6
Electrons per shell2, 8, 8
Physical properties
Phase at STPgas
Melting point83.81 K ​(−189.34 °C, ​−308.81 °F)
Boiling point87.302 K ​(−185.848 °C, ​−302.526 °F)
Density (at STP)1.784 g/L
when liquid (at b.p.)1.3954 g/cm3
Triple point83.8058 K, ​68.89 kPa[3]
Critical point150.687 K, 4.863 MPa[3]
Heat of fusion1.18 kJ/mol
Heat of vaporization6.53 kJ/mol
Molar heat capacity20.85[4] 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 statescommon: (none)
ElectronegativityPauling scale: no data
Ionization energies
  • 1st: 1520.6 kJ/mol
  • 2nd: 2665.8 kJ/mol
  • 3rd: 3931 kJ/mol
  • (more)
Covalent radius106±10 pm
Van der Waals radius188 pm
Color lines in a spectral range
Spectral lines of argon
Other properties
Natural occurrenceprimordial
Crystal structureface-centered cubic (fcc) (cF4)
Lattice constant
Face-centered cubic crystal structure for argon
a = 546.91 pm (at triple point)[5]
Thermal conductivity17.72×10−3  W/(m⋅K)
Magnetic orderingdiamagnetic[6]
Molar magnetic susceptibility−19.6×10−6 cm3/mol[7]
Speed of sound323 m/s (gas, at 27 °C)
CAS Number7440-37-1
History
Discovery and first isolationLord Rayleigh and William Ramsay (1894)
Isotopes of argon
Main isotopes[8] Decay
abun­dance half-life (t1/2) mode pro­duct
36Ar 0.334% stable
37Ar trace 35 d ε 37Cl
38Ar 0.0630% stable
39Ar trace 268 y β 39K
40Ar 99.6% stable
41Ar trace 109.34 min β 41K
42Ar synth 32.9 y β 42K
 Category: Argon
| references
Ar · Argon
Cl ←

ibox Cl

iso
18
Ar  [e]
IB-Ar [e]
IBisos [e]
→ K

ibox K

indexes by PT (page)
child table, as reused in {IB-Ar}
Main isotopes of argon
Main isotopes[8] Decay
abun­dance half-life (t1/2) mode pro­duct
36Ar 0.334% stable
37Ar trace 35 d ε 37Cl
38Ar 0.0630% stable
39Ar trace 268 y β 39K
40Ar 99.6% stable
41Ar trace 109.34 min β 41K
42Ar synth 32.9 y β 42K
Data sets read by {{Infobox element}}
Name and identifiers
Symbol etymology (11 non-trivial)
Top image (caption, alt)
Pronunciation
Allotropes (overview)
Group (overview)
Period (overview)
Block (overview)
Natural occurrence
Phase at STP
Oxidation states
Spectral lines image
Electron configuration (cmt, ref)
Isotopes
Standard atomic weight
  most stable isotope
Wikidata
Wikidata *
* Not used in {{Infobox element}} (2023-01-01)
See also {{Index of data sets}} · Cat:data sets (46) · (this table: )

References

  1. ^ "Standard Atomic Weights: Argon". CIAAW. 2017.
  2. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  3. ^ a b Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.121. ISBN 1-4398-5511-0.
  4. ^ 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.
  5. ^ Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
  6. ^ 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.
  7. ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  8. ^ a b 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.

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 2016 (from subtemplates used by {{Infobox element}})
  • <ref name="b92" /> for the source edited by Haynes