The bond order of the acetylide ion HC≡C− is 3, indicating a triple bond between the carbon atoms.
The acetylide ion consists of two carbon atoms with a triple bond between them and a negative charge. In the triple bond, there are six bonding electrons (two pi bonds and one sigma bond) and zero antibonding electrons.
Among the given options NO+ will have the same bond order and magnetic property like acetylide ion.
| Species | Bond Order | Magnetic moment |
| HC≡C− | 3 | 0 |
| O2+ | 2.5 | 3B.M |
| N2+ | 2.5 | 3B.M |
| NO+ | 3 | 0 |
| O2− | 1.5 | 3B.M |