The bond order of a diatomic species can be calculated using molecular orbital theory as follows,
Bondorder=2No.ofBMOelectrons−No.ofABMOelectrons
BMO = bonding molecular orbital
ABMO = Anti bonding molecular orbital.
Based on the total number electrons in bond orders are given in the following table.
| Number of e− | Bond order |
| 13 | 2.5 |
| 14 | 3 |
| 15 | 2.5 |
| 16 | 2 |
CN−,NO+andO22+ are having 14 electrons each, hence the bond order is 3.