What is the Difference Between Bonding and Antibonding Molecular Orbitals?

Bonding and antibonding molecular orbitals are formed when atomic orbitals of two atoms combine to create molecular orbitals. The main differences between these orbitals are:

1. Electron density: In bonding orbitals, electrons spend most of their time between the nuclei of the two atoms, leading to an increase in electron density between the nuclei. In antibonding orbitals, electrons spend most of their time outside the nuclei of the two atoms, leading to a decrease in electron density between the nuclei.
2. Energy levels: Bonding molecular orbitals are always lower in energy (more stable) than the component atomic orbitals, while antibonding molecular orbitals are always higher in energy (less stable) than the component atomic orbitals.
3. Stability: Placing electrons in bonding orbitals stabilizes the molecule, as the electron density between the nuclei increases. Conversely, placing electrons in antibonding orbitals decreases the stability of the molecule, as the electron density between the nuclei decreases.
4. Contribution to molecular shape: Bonding molecular orbitals represent the shape of the molecule, while antibonding molecular orbitals do not contribute to the shape of the molecule.

In general, electrons in bonding orbitals pull the nuclei closer together, grouping atoms as a molecule and increasing bond order. On the other hand, electrons in antibonding orbitals pull the nuclei away from each other, decreasing bond order.

Comparative Table: Bonding vs Antibonding Molecular Orbitals

The main difference between bonding and antibonding molecular orbitals lies in their energy levels, electron density, and stabilization of the molecule. Here is a comparison table highlighting the key differences:

Bonding orbitals are formed when electrons spend most of their time between the nuclei of two atoms, resulting in an increase in electron density between the nuclei. This leads to a stabilization of the molecule. On the other hand, antibonding orbitals are formed when electrons spend most of their time outside the nuclei of two atoms, leading to a decrease in electron density between the nuclei and destabilizing the molecule.