Argon is the chemical element of atomic number 18, symbol Ar. It belongs to the group of noble gases, with helium, neon, krypton, xenon, radon. Argon is mostly used as an inert shielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive. Argon is also used in incandescent, fluorescent lighting, and other gas-discharge tubes. Argon makes a distinctive blue-green gas laser.