Atoms that have filled outermost energy levels and do not participate in chemical bonding are called

Inert: Since their outermost electron shells (valence shells) are completely filled, they have little tendency to acquire or lose electrons which prevents them from bonding. On the opposite note, an atom that has an incompletely filled valence shell will be likely be more reactive, in an effort to achieve a filled-outermost energy level.

The higher you go up the less oxygen there is