MO Configuration ($$> 14$$ electrons, e.g., $$\text{O}_2, \text{F}_2$$)

Energy Order: $$\sigma_{1s} < \sigma^*_{1s} < \sigma_{2s} < \sigma^*_{2s} < \sigma_{2p_z} < (\pi_{2p_x} = \pi_{2p_y}) < (\pi^*_{2p_x} = \pi^*_{2p_y}) < \sigma^*_{2p_z}$$

Concept: Outlines the standard energy ordering for heavier diatomic molecules where the energy gap between $$\text{2s}$$ and $$\text{2p}$$ atomic levels is large enough to prevent significant orbital mixing.

Notation:

• $$\sigma, \pi$$ = Bonding molecular orbitals;
• $$\sigma^*, \pi^*$$ = Antibonding molecular orbitals;
• $$x, y, z$$ = Spatial orientations of the atomic $$p$$-orbitals.