Why Are Rare Gases Stable?
Rare gases are the most stable because they have the maximum number of valence electrons that their outer shell can accommodate. This means that rare gases have an octet configuration.
Noble gas elements are stable and unreactive (inert) because their outer valence shells are filled with eight electrons.
If the outer s- and p-orbitals are filled and the octet rule is followed, the noble gas elements do not tend to gain or lose electrons in the bonding process.