A colorless, odorless, highly unreactive gaseous element, which is the third most abundant gas in Earth's atmosphere (making up approximately 1 percent of the atmosphere). It is obtained commercially by fractionation of liquid air. Argon is one of the inert gases. It is used in electric lights, fluorescent tubes, electronic valves, and as an inert-gas shield in arc-welding.
The discovery of argon was announced Lord Rayleigh and William Ramsay at Oxford in 1894. Its name comes from the Greek argos, meaning "inactive".