# How can I read molecular orbital diagram?

Apr 14, 2014

WARNING. This is a long answer.

Let's analyze a molecular orbital (MO) diagram for CO.

Points to Note:

1. Individual atomic orbitals (AOs) are on the far left (C) and far right (O) of the diagram.

2. These AOs overlap to produce the MOs of CO in the middle. The MOs are either σ or π orbitals. They are bonding, nonbonding, or antibonding.

Conservation of Orbitals:

The overlap of two AOs produces two MOs, one bonding and one antibonding.

a. The overlap of two s AOs produces a σ MO and a σ* MO.

b. The end-on overlap of two p AOs produces a σ MO and a σ* MO.

c. The side-on overlap of two p AOs produces a π MO and a π* MO.

Interpreting the Diagram:

1. The 2s orbitals of C and O overlap to form the σ(2s) and σ*(2s) orbitals of CO.

2. The $2 {p}_{z}$ orbitals of C and O overlap end-on to form the σ(2p) and σ*(2p) orbitals of CO.

3. The $2 {p}_{x}$ orbitals of C and O overlap side-on to form one set of π(2p) and π*(2p) orbitals for CO.

4. The $2 {p}_{y}$ orbitals of C and O overlap side-on to form a second set of π(2p) and π(2p) orbitals of CO. These two sets of orbitals are degenerate* (they have the same energy).