argon (är`gŏn) [Gr.,=inert], gaseous chemical element; symbol Ar; at. no. 18; at. wt. 39.948; m.p. −189.2°C;; b.p. −185.7°C;; density 1.784 grams per liter at STP STP or standard temperature and pressure, standard conditions for measurement of the properties of matter. The standard temperature is the freezing point of pure water, 0°C; or 273.15°K;.
..... Click the link for more information. ; valence 0. Argon is a colorless, odorless, tasteless gas occurring in air (of which it constitutes 0.94% by volume) and in some volcanic gases. It is a member of Group 18 of the periodic table periodic table, chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley . In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the
..... Click the link for more information. , a group called the noble or inert gases inert gas or noble gas, any of the elements in Group 18 of the periodic table . In order of increasing atomic number they are: helium , neon , argon , krypton , xenon , and radon .
..... Click the link for more information. from the mistaken former belief that none of its members could form chemical compounds; in fact, other members of the group, e.g., krypton, xenon, and radon, do form compounds. Argon is prepared by fractional distillation of liquid air. Its extreme inertness has caused it to be substituted for nitrogen in electric light bulbs. It is mixed with neon in so-called neon signs (gas discharge tubes) to produce a green-to-blue glow. It is used as a protective atmosphere in arc welding, in the refining of reactive elements, and in the growing of crystals for use in semiconductor devices. Argon was first obtained by Lord Rayleigh and Sir William Ramsay in 1894. Previously Lord Rayleigh had noticed that a liter of supposedly pure nitrogen drawn from the air weighed more than a liter prepared from a nitrogen compound. This difference in weight led him to conclude that another gas was present in the supposedly pure nitrogen. Actually several unreactive gases were present; the first samples of "argon" also contained helium helium (hē`lēəm), gaseous chemical element; symbol He; at. no. 2; at. wt. 4.0026; m.p.
..... Click the link for more information. , neon neon (nē`ŏn) [Gr.,=new], gaseous chemical element; symbol Ne; at. no. 10; at. wt. 20.179; m.p. −248.67°C;; b.p. −246.
..... Click the link for more information. , krypton krypton (krĭp`tŏn) [Gr.,=hidden], gaseous chemical element; symbol Kr; at. no. 36; at. wt. 83.80; m.p. −156.6°C;; b.p.
..... Click the link for more information. , and xenon xenon (zē`nŏn) [Gr.,=strange], gaseous chemical element; symbol Xe; at. no. 54; at. wt. 131.29; m.p. −111.9°C;; b.p.
..... Click the link for more information. . Ramsay obtained pure argon later by evaporating it from liquid air.

argon

Chemical element, chemical symbol Ar, atomic number 18. Colourless, odourless, and tasteless, it is the most abundant of the noble gases on Earth and the one most used in industry. It constitutes about 1% of air and is obtained by distillation of liquid air. Argon provides an inert gas shield in welding and brazing, in lightbulbs and lasers, in Geiger counters, and in the production and fabrication of certain metals. Because a radioactive form of argon is produced by decay of a naturally occurring radioactive potassium isotope, it can be used to date rocks and samples more than 100,000 years old.

argon

an extremely unreactive colourless odourless element of the rare gas series that forms almost 1 per cent (by volume) of the atmosphere. It is used in electric lights. Symbol: Ar; atomic no.: 18; atomic wt.: 39.948; density: 1.7837 kg/m³; freezing pt.: --189.3°C; boiling pt.: --185.9°C

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