What is bond order?
Bond order describes the number of chemical bonds between a pair of atoms. In molecular orbital theory, it's calculated from the number of electrons in bonding vs. antibonding orbitals.
Bond Order = (Bonding e⁻ − Antibonding e⁻) / 2
A bond order of 1 = single bond, 2 = double bond, 3 = triple bond. A bond order of 0 means no stable bond exists.
Bond order and stability
Higher bond order = shorter bond length, higher bond energy, greater stability. For example, N₂ has a bond order of 3 (triple bond) and is extremely stable, while He₂ has a bond order of 0 and doesn't exist.