Draw an MO energy diagram for CO. (Use the energy ordering of O₂.) Predict the bond order and make a sketch of the lowest energy bonding molecular orbital.

Key Concepts

Molecular Orbital Theory

Molecular Orbital (MO) Theory describes how atomic orbitals combine to form molecular orbitals that can be occupied by electrons. In this theory, electrons are delocalized over the entire molecule rather than being confined to individual atoms. The energy levels of these molecular orbitals are determined by the energies of the atomic orbitals involved in their formation, leading to bonding and antibonding interactions.

Bond Order

Bond order is a measure of the number of chemical bonds between a pair of atoms, calculated as the difference between the number of bonding and antibonding electrons divided by two. It provides insight into the stability and strength of a bond; a higher bond order indicates a stronger bond. For example, a bond order of 1 corresponds to a single bond, while a bond order of 2 indicates a double bond.

Energy Ordering of Molecular Orbitals

The energy ordering of molecular orbitals is crucial for predicting the electronic structure of a molecule. For diatomic molecules like CO, the relative energies of the molecular orbitals can be influenced by the atomic orbitals of the constituent atoms. In the case of CO, the energy ordering follows that of O2, where the σ2s and σ*2s orbitals are lower in energy than the σ2p and π2p orbitals, affecting the overall bond characteristics.