Argon

Argon (Ar) is a chemical element belonging to the group of noble gases on the periodic table. Its atomic number is 18. In its standard state it is a colorless, odorless, and tasteless gas. It exhibits low chemical reactivity because its outermost electron shell is complete.

Argon is the third most abundant gas in Earth's atmosphere, after nitrogen and oxygen. It comprises approximately one percent of the volume of air. Because of its inertness, it is used to create an inert atmosphere when oxidation needs to be prevented.

Properties

Argon is denser than air. It has low boiling and melting points, meaning it exists as a liquid only at extremely low temperatures. Its noble gas group includes helium, neon, krypton, xenon, and radon. Argon does not form ordinary chemical compounds under normal conditions.

Extraction

Argon is produced commercially from air using cryogenic distillation. Air is cooled until it liquefies, then its different components are separated at their different boiling points. Most of the argon occurring naturally in air comes from the radioactive decay of potassium-40 in Earth's rocks.

Uses

Argon is used in welding—particularly for steel and aluminum—where it prevents air from contaminating the weld area. It is also used to fill certain lamps and is employed in double-pane windows to reduce heat transfer. Semiconductor manufacturing and analytical laboratories also use it.