What is unreactive gas?
A gas that rarely to never reacts violently with other elements.
The unreactive gases are called the Noble Gases and appear in the rightmost column of the Periodic Table of the Elements. From lightest to heaviest they are:- Helium (He) Neon (Ne) Argon (Ar) Krypton (Kr) Xenon (Xe) Radon (Rn) which is radioactive. There are also a large number of unreactive gases which are compounds.