Bond Order

Bond Order

In the Lawis description of covalent bond, the Bond Order is given by the number of bonds between the two atoms in a molecule. The bond order, for example in H₂ (with a single shared electron pair), in O₂ (with two shared electron pairs) and in N₂ (with three shared electron pairs) is 1,2,3 respectively. Similarly in CO (three shared electron pairs between C and O) the bond order is 3. For N₂, bond order is 3 and its ∆_aH^v is 946kJ mol1; being one of the highest for a diatomic molecule.

Isoelectronic molecules and ions have identical bond orders; for example, F2 and O₂^2- have bond order 1. N₂, CO and NO⁺ have bond order 3.

A general correlation useful for understanding the stabilities of molecules is that: with increase in bond order, bond enthalpy increases and bond length decreases.