Any of the so-called "Noble Gases" from the Periodic Table of the Elements. These elements normally do not combine with other elements. They are useful as buffers against chemical interactions, and appear to have interesting properties related to scalar-field interactions. The gases and their atomic numbers are: Helium 2, Neon 10, Argon 18, Krypton 36, Xenon 54, and Radon 86.