Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of theperiodic table and is a noble gas. Argon is the third most abundant noble gas in Earth's crust.

Argon is produced industrially by the fractional distillation of liquid air. Argon is mostly used as an inert shielding 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 inincandescent, fluorescent lighting, and other gas discharge tubes. Argon makes a distinctiveblue-green gas laser. Argon is also used in fluorescent glow starters.