The chemical element with the symbol 'Ar' is argon. Argon is a colorless, odorless, and inert noble gas found in the atmosphere at about 0.93% concentration. It is the third most abundant gas in the Earth's atmosphere, after nitrogen and oxygen. Argon is commonly used in various applications, including providing an inert gas environment for welding, in incandescent and fluorescent lighting, and as a protective atmosphere in growing crystals of semiconductors. Its chemical stability and non-reactive nature make it valuable in many industries, particularly those requiring an absence of chemical reactions.