A colorless, odorless, inert, gaseous chemical element. Argon has an atomic number of 18 and an atomic weight of 39.998. The symbol for argon is Ar.

Argon is commonly used to fill electric light bulbs and the envelopes of electron tubes. The argon takes the place of air, which contains oxygen, and by keeping oxygen away from the hot filaments in the bulbs and tubes, the filaments will not burn out, or oxidize.