Here are the MO schemes of NX2NX2 (left) and OX2OX2 (right).
Why is the σ-MO formed by the p AOs energetically above the π-MO for NX2 but not for OX2?
Can it be explained this way:
In second period elements with more than a half filled p orbitals, the energy pattern of the MOs is regular.
In second period elements with less than or half filled p orbitals, as the s and p atomic orbitals have similar energies, so the formed σXg MO would have similar energy as σXu, but because of electron cloud repulsion it has a big increase in energy, hence it is above the π orbitals? And this phenomenom is known as sp mixing.
Or am I wrong somewhere? Is my reasoning corret?
