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Argon, 18Ar
Vial containing a violet glowing gas
Pronunciation/ˈɑːrɡɒn/ (AR-gon)
Appearancecolorless gas exhibiting a lilac/violet glow when placed in an electric field
Standard atomic weight Ar, std(Ar)[39.79239.963] conventional: 39.95[1][2]
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


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 states0
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)
Face-centered cubic crystal structure for argon
Speed of sound323 m/s (gas, at 27 °C)
Thermal conductivity17.72×103  W/(m⋅K)
Magnetic orderingdiamagnetic[5]
Molar magnetic susceptibility−19.6·10−6 cm3/mol[6]
CAS Number7440-37-1
Discovery and first isolationLord Rayleigh and William Ramsay (1894)
Main isotopes of argon
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
36Ar 0.334% stable
37Ar syn 35 d ε 37Cl
38Ar 0.063% stable
39Ar trace 269 y β 39K
40Ar 99.604% stable
41Ar syn 109.34 min β 41K
42Ar syn 32.9 y β 42K
and 38
content may be as high as 2.07% and 4.3% respectively in natural samples. 40
is the remainder in such cases, whose content may be as low as 93.6%.
 Category: Argon
| 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.

Chemistry[change | change source]

Argon atoms are found in air. About 1% of the Earth's atmosphere (the air around us) is argon. It is not toxic and it does not burn easily.[7] Not many compounds can be made from Argon. However, some compounds have been formed, like argon fluorohydride (HArF). Argon is a heavier gas than helium, so if a balloon is filled with argon, it would fall the the ground.

History[change | change source]

Argon was first removed from air in 1894 by Lord Rayleigh and Sir William Ramsay at University College London by removing oxygen, carbon dioxide, water, and nitrogen from a sample of clean air.[8][9]

Isotopes[change | change source]

The main isotopes of argon found on Earth are 40Ar (99.6%), 36Ar (0.34%), and 38Ar (0.06%). The most abundant isotope of argon is 40Ar. But other planets have different isotopes of argon.[10]

Production[change | change source]

Argon is gotten industrially by the fractional distillation of liquid air. About 700,000 tonnes of argon are produced worldwide every year.[11][10]

40Ar is made by the decay of 40K with a half-life of 1.25 billion years by electron capture or positron emission. Because of this, it is used in knowing how old rocks are.

Uses[change | change source]

Argon is often used when welding steel and similar work, to push away the air around the weld, so the oxygen in the air can't join with the metal being welded. It can also be used in neon lights for a purple color. Argon is used in the poultry industry to asphyxiate birds.[12][13] Argon is sometimes used for extinguishing (ending) fires.[14]

Liquid argon is used in neutrino experiments and looking for dark matter. Argon is used to preserve food.[15] Argon is sometimes used as the propellant in aerosol cans. Argon is also used as a preservative for such products as varnish, polyurethane, and paint. Argon has been used by athletes as a doping agent and has been banned as use.[16] It is used to know how old rocks are.

Related pages[change | change source]

Sources[change | change source]

  1. "IUPAC Periodic Table of the Elements and Isotopes". King's Center for Visualization in Science. IUPAC, King's Center for Visualization in Science. Retrieved 8 October 2019.
  2. "Standard Atomic Weights: Argon". CIAAW. 2017.
  3. 3.0 3.1 Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.121. ISBN 1439855110.
  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. 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.
  6. Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  7. "Universal Industrial Gases, Inc. ... MSDS Gaseous Argon - GAR". Retrieved 2021-08-29.
  8. "I. Argon, a new constituent of the atmosphere". Proceedings of the Royal Society of London. 57 (340–346): 265–287. 1895-12-31. doi:10.1098/rspl.1894.0149. ISSN 0370-1662. S2CID 123541469.
  9. "The Nobel Prize in Chemistry 1904". Retrieved 2021-08-29.
  10. 10.0 10.1 Emsley, John (2011). Nature's Building Blocks : an a-Z Guide to the Elements (2nd ed.). Oxford: Oxford University Press, Incorporated. ISBN 978-0-19-257046-8. OCLC 1119634122.
  11. "Periodic Table of Elements: Argon - Ar (". Retrieved 2021-08-29.
  12. "Slaughter technology" (PDF). 2011-07-24. Archived (PDF) from the original on 2011-07-24. Retrieved 2021-08-29.
  13. Shields, Sara J.; Raj, A. B. M. (2010-09-17). "A Critical Review of Electrical Water-Bath Stun Systems for Poultry Slaughter and Recent Developments in Alternative Technologies". Journal of Applied Animal Welfare Science. 13 (4): 281–299. doi:10.1080/10888705.2010.507119. ISSN 1088-8705. PMID 20865613. S2CID 11301328.
  14. Su, Joseph Z.; Kim, Andrew K.; Crampton, George P.; Liu, Zhigang (2001-05-01). "Fire Suppression with Inert Gas Agents". Journal of Fire Protection Engineering. 11 (2): 72–87. doi:10.1106/X21V-YQKU-PMKP-XGTP.[permanent dead link]
  15. Ilouga, Pierre E.; Winkler, Dirk; Kirchhoff, Christian; Schierholz, Bernd; Wölcke, Julian (2007). "Investigation of 3 Industry-Wide Applied Storage Conditions for Compound Libraries". Journal of Biomolecular Screening. 12 (1): 21–32. doi:10.1177/1087057106295507. ISSN 1087-0571. PMID 17099243. S2CID 23750770.
  16. "Newsroom". World Anti-Doping Agency. Archived from the original on 2021-04-27. Retrieved 2021-08-29.