The chemical symbol for argon is Ar. Argon is a noble gas and is colorless, odorless, and inert under most conditions, which makes it valuable in many industrial applications. It is commonly used in welding and in lighting, as well as in providing an inert atmosphere for sensitive chemical reactions and processes. Argon is abundant in the Earth's atmosphere, making up about 0.93% of it, and was first isolated in 1894 by the British scientist Lord Rayleigh and the Scottish chemist William Ramsay.