Argon is an element that belongs to the noble gas family. It has an atomic number of 18 and is known by the atomic symbol Ar. It has a freezing point of -308.7°F (-189.3°C), a boiling point of -302.6°F (-185.9°C) and an atomic weight of 39.948.

Argon might have been discovered more than a hundred years earlier if a scientific instrument, the spectroscope, had been invented sooner. The story of argon's discovery began in the 1780s, when Henry Cavendish tried repeatedly to combine oxygen with nitrogen, but always had a small bubble of gas left over. Although Cavendish speculated that this was some kind of nonreactive gas, he lacked the technology with which to analyze it. As it turned out, this bubble would contain five gases comprising a new class of elements that scientists had never before imagined.

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