Antibonding MO

Antibonding MO Definition:

The Antibonding MO is the higher energy molecular orbital resulting from the destructive interference between atomic orbitals.

Antibonding MO Explained:

Molecular orbitals are used to describe the role of electrons in an entire molecule. Many different electrons clouds are present in different molecules because of the different bonding. These electron clouds contain electrons that provide important information such as energy and reactivity. The presence of electrons in antibonding MO weakens the bond, creating high energy thus forming one or more nodes between the atoms. As a result, there is a repulsive force that tends to separate/break the bonds within the molecule.

  • The antibonding MO has a negative value for the wavefunction.
  • Also written as σ∗ (for sigma bonds), the antibonding MO is asymmetric with respect to the middle point of the bond, this sometimes called asymmetric.

Example – s- atomic orbital overlap (left), p-atomic orbital overlap (right). Note, both the overlaps represent sigma bonding. The p-orbitals can also be involved in pi-bonding, in which case the diagram must also show the pi-bonded molecular orbitals.