this article is about the chemical element. for other uses, see argon (disambiguation).
chemical element with atomic number 18
colorless gas exhibiting a lilac/violet glow when placed in an electric field
standard atomic weightar, std(ar)
[39.792, 39.963] conventional: 39.95
argon in the periodic table
ne ↑ ar ↓ kr
chlorine ← argon → potassium
group 18 (noble gases)
[ne] 3s2 3p6
electrons per shell
2, 8, 8
83.81 k (−189.34 °c, −308.81 °f)
87.302 k (−185.848 °c, −302.526 °f)
when liquid (at b.p.)
83.8058 k, 68.89 kpa
150.687 k, 4.863 mpa
heat of fusion
heat of vaporization
molar heat capacity
pauling scale: no data
1st: 1520.6 kj/mol
2nd: 2665.8 kj/mol
3rd: 3931 kj/mol
van der waals radius
spectral lines of argon
face-centered cubic (fcc)
speed of sound
323 m/s (gas, at 27 °c)
discovery and first isolation
lord rayleigh and william ramsay (1894)
main isotopes of argon
36 ar and 38 ar content may be as high as 2.07% and 4.3% respectively in natural samples. 40 ar is the remainder in such cases, whose content may be as low as 93.6%.
argon is a chemical element with the symbolar and atomic number 18. it is in group 18 of the periodic table and is a noble gas. argon is the third-most abundant gas in the earth's atmosphere, at 0.934 % (9340 ppmv). it is more than twice as abundant as water vapor (which averages about 4 000 ppmv, but varies greatly), 23 times as abundant as carbon dioxide (400 ppmv), and more than 500 times as abundant as neon (18 ppmv). argon is the most abundant noble gas in earth's crust, comprising 0.00015 % of the crust.
nearly all of the argon in the earth's atmosphere is radiogenicargon-40, derived from the decay of potassium-40 in the earth's crust. in the universe, argon-36 is by far the most common argon isotope, as it is the most easily produced by stellar nucleosynthesis in supernovas.
the name "argon" is derived from the greek word ἀργόν, neuter singular form of ἀργός meaning "lazy" or "inactive", as a reference to the fact that the element undergoes almost no chemical reactions. the complete octet (eight electrons) in the outer atomic shell makes argon stable and resistant to bonding with other elements. its triple point temperature of 83.8058 k is a defining fixed point in the international temperature scale of 1990.
argon is produced industrially by the fractional distillation of liquid air. argon is mostly used as an inertshielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive; for example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning. argon is also used in incandescent, fluorescent lighting, and other gas-discharge tubes. argon makes a distinctive blue-green gas laser. argon is also used in fluorescent glow starters.
The name "argon" is derived from the Greek word ἀργόν, neuter singular form of ἀργός meaning "lazy" or "inactive", as a reference to the fact that the element undergoes almost no chemical reactions. The complete octet (eight electrons) in the outer atomic shell makes argon stable and resistant to bonding with other elements. Its triple point temperature of 83.8058 K is a defining fixed point in the International Temperature Scale of 1990.