A noble question

[ConceptuallyInept]

This may be more of a chemistry question than a physics one, but why does glass tubing filled with a noble gas emit coloured light when electric current flows through the tube. Being inert I would've thought they would be the least likely substance to exhibit such a property.

Cheers

[HallsofIvy]

Why would you think that? Being "noble" means that it does not react with other elements, not that it doesn't "lose" electrons.