An inert gas is one which does not react with other elements. The Noble gases and Nitrogen often do not react with many substances. Reed Switches are filled with a a mixture of inert gases to exclude contaminants, prevent oxidation of the contacts, and to prevent ice formation in low temperature applications.
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.
Purified argon gas is the most commonly used inert gas due to its high natural abundance (78.3% N2, 1% Ar in air) 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. This is a tendency, not a rule, as all noble gases and other "inert" gases can react to form compounds under some conditions.
