inert (chemistry) – a substance that shows little or no reactivity

(pronounced in-ert)

To remember the meaning of inert (chemistry), use the following mnemonic:

He fell in and hurt (inert) himself but showed no reaction. 

Inert means chemically unreactive or very stable. The most common examples of inert substances are the noble gases, such as helium, neon, and argon, which are found in group 0 of the periodic table. Noble metals including gold, platinum, and silver which are also very unreactive. The metals are resistant to corrosion, oxidation and reaction with air under normal conditions, which is why they are used for jewellery. Noble gases are less reactive than even gold. While gold is a highly inert metal it can form compounds and alloys under specific conditions. Noble gases however are almost entirely inert or "noble".

To see more about inert gases and their molecular make-up, see the page noble gases.