Bonding Molecular Orbital
A molecular orbital lower in energy than the atomic orbitals from which it forms, whose occupation stabilises the molecule.
Formula / equation
ψ = ψ_A + ψ_B
Unit
Dimensionless
In depth
Constructive interference of the atomic wavefunctions builds up electron density between the nuclei, screening their repulsion and pulling them together. Bonding orbitals have no node between the nuclei, and every electron placed in one contributes half a unit to the bond order.
Examples in the real world
The σ1s orbital of H₂, which holds both electrons and gives a bond order of one.