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. The noble gases often do not react with many substances^[1] and were historically referred to as the inert gases. Inert gases are used generally to avoid unwanted chemical reactions degrading a sample. These undesirable chemical reactions are often oxidation and hydrolysis reactions with the oxygen and moisture in air. The term inert gas is context-dependent because several of the noble gases can be made to react under certain conditions. Helium, Neon, Argon, Krypton, Xenon, Radon are the six inert ( noble ) gases

Purified argon gas is the most commonly used inert gas due to its high natural abundance (78.3% N₂, 1% Ar in air ^[2]) 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.^[3] This is a tendency, not a rule, as all noble gases and other "inert" gases can react to form compounds under some conditions.