Argon (Ar) is a chemical element with atomic number (Z) 18, group 18, period 3, and atomic weight 39.948. The Argon (Ar) is the chemically inert element that is colourless and odourless in both its liquid and gaseous forms. Argon is not found in any compounds, used in lighting and as an inert gas shield in arc welding and cutting. (Refer to the Chemical Element; Periodic Table)