Helium, neon, argon, krypton, xenon and radon are situated in group 18 of the periodic table, and are known collectively as the noble or inert gases. Both names refer to the difficulty with which the elements form compounds.
This inertness of the gases is their most striking characteristic, and is a result of their extremely stable electronic configuration. All the gases have a full outer shell of eight electrons - a state to which all elements aspire - and thus are loath to give up an electron, or to make room for electrons donated by other elements. Not all of the gases, however, are completely inert. Xenon, krypton and radon are capable of forming compounds, although the radioactivity of radon makes this very difficult.
All of the gases are odourless, tasteless and colourless. Passing an elelctric current through them, however, can produce a characteristic glow. Neon, famously, glows orange-red.
