Noble Gases

Synonyms

Rare gases

Definition

The noble gases are a group of chemical elements with a very low chemical reactivity. In most natural conditions, they cannot form chemical compounds and their abundances and isotopic ratios are only affected by physical processes such as phase changes, kinetic effects, and nuclear reactions including radioactivity. Due to their inertness, they are used as cosmochemical and geochemical tracers when investigating the origin and the processing of their host phases or of other volatile elements.

Overview

The noble gases – helium (symbol: He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) – have all their electronic shells saturated and therefore cannot readily make compounds. Radon isotopes are all instable and this element is generally not used as a geochemical tracer. Although they are abundant in stars (helium is the second most abundant element in the universe), they are highly depleted in metals and silicates, and therefore in inner...