Antibonding Molecular Orbital
A molecular orbital higher in energy than its parent atomic orbitals, whose occupation destabilises the molecule.
Formula / equation
ψ* = ψ_A − ψ_B
Unit
Dimensionless
In depth
Destructive interference creates a node between the nuclei, removing electron density from where it would bind them and exposing the nuclei to mutual repulsion. Marked with an asterisk, antibonding orbitals are destabilised slightly more than the corresponding bonding orbitals are stabilised.
Examples in the real world
He₂ would place two electrons in σ*1s, cancelling the bonding pair and giving bond order zero — so He₂ does not exist.