Noble gases

From Glossary of Meteorology

noble gases

(Also called rare gases, inert gases.) The elements helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) that make up the eighth period of the periodic table.

Because of their completely filled atomic orbitals, these gases are extremely nonreactive, and build up to measurable concentrations in the atmosphere.