Inert gas

An inert gas is a gas that does not readily undergo chemical reactions with other chemical substances and therefore does not readily form chemical compounds. Though inert gases have a variety of applications, they are generally used to prevent unwanted chemical reactions with the oxygen (oxidation) and moisture (hydrolysis) in the air from degrading a sample. Generally, all noble gases except oganesson (helium, neon, argon, krypton, xenon, and radon), nitrogen, and carbon dioxide are considered inert gases. The term inert gas is context-dependent because several of the noble gases, including nitrogen and carbon dioxide, can be made to react under certain conditions.^[1][2]

Purified argon gas is the most commonly used inert gas due to its high natural abundance (78.3% N₂, 1% Ar in air)^[3] and low relative cost.

Unlike noble gases, an inert gas is not necessarily elemental and is often a compound gas. Like the noble gases, the tendency for non-reactivity is due to the valence, the outermost electron shell, being complete in all the inert gases.^[4] This is a tendency, not a rule, as all noble gases and other "inert" gases can react to form compounds under some conditions.