Most inert element

Helium heads the noble gases in the Periodic Table, and having a valence of zero, it is chemically reactive under all normal conditions. In its normal gaseous state, it is an electrical insulator, though can remain ionised to emit light as is demonstrated by all of the noble gasses (helium – He, neon – Ne, argon – Ar, krypton – Kr, xenon – Xe, and radon – Rn). Helium is produced naturally by the decay of radium components.