How many valence electrons are found in most atoms of the noble gases? How would you use this information to explain why the noble gases are non-reactive?
8, not energetically favourable to release electrons, shells are full so can't gain more.
Remember that all noble gases are free from being involved in reactions as they are stable, all elements strive to be stable, I.E have a full outer shell of electrons, noble gases already do, so don't undergo any reactions, He is the only one with a full shell at 2 by the way :)
Think of NaCl in this way, sodium has 1 electron in it's outer shell, Cl has 7, 1+7 is 8 therefore is a "stable compound"