has the 1S and 2S levels filled giving
as a base.
It has four valence 2P electrons which we will treat as two valence 2P holes.
Hund's first rule , maximum total
, tells us to couple the two hole
This is the symmetric spin state so we'll need to make the space state antisymmetric.
Hund's second rule, maximum
, doesn't play a role because only the
state is antisymmetric.
Since the shell is more than half full we couple to the the highest
So the ground state is
Oxygen Ground State