Argon is a gaseous chemical element which makes up almost one percent of the Earth's atmosphere. Among the noble gases, argon is generally considered to be the most abundant, and it is sometimes used to replace other noble gases in situations where an inert gas in needed. The relatively nonreactive gas has a number of industrial uses, and argon isotopes are also used in radiocarbon dating for very old artifacts. Consumers may interact with argon now and then, primarily indirectly.

Like other noble gases such as helium, neon, and krypton, argon was initially believed to be totally inert. In fact, the gas will react in certain situations, forming some compounds, but it is remarkably stable otherwise. Argon is colorless, odorless, and tasteless, and in its pure form argon is nontoxic, although the gas can act as an asphyxiant if it displaces the oxygen in a room. On the periodic table of elements, Argon is identified by the symbol Ar, and the gas has an atomic number of 18.

The gas was discovered in 1894 by Sir William Ramsay and Lord Rayleigh. The men had earlier noticed that a sample of nitrogen from the air appeared to be heavier than nitrogen extracted from other sources, and they theorized that the nitrogen might actually be mixed with other gases. Experimentation proved this theory correct, and they named the gas they discovered argon, named after the Greek argos, or “lazy one,” in a reference to the low reactivity of the gas.

Later, it was realized that the sample of air which had been termed “argon” was actually a sample of several noble gases. Ramsay managed to extract pure argon later. Ramsay also performed research on other noble gases, confirming the findings of other scientists and making a few new discoveries of his own. In 1904, both Ramsay and Rayleigh received the Nobel Prize in Chemistry for their work on the noble gases.

Commercially, argon is extracted through the fractional distillation process, which involves cooling air until it liquefies and then heating it, forcing the separate gases to precipitate out. Argon is usually relatively cheap, since it is a byproduct of the large market for oxygen and nitrogen. The gas is frequently used in lighting, often in combination with other noble gases, and it is also used to create a shield for arc welding. Electronics companies also use argon in their fire extinguishers, as the gas can put out a fire without damaging equipment.