The bond order of the nitrate ion (NO3–) is 1.33. To understand this, we need to look at its Lewis structure and the concept of resonance.
In the case of NO3–, the molecule has three equivalent resonance structures. Each of these structures features one nitrogen-oxygen double bond and two nitrogen-oxygen single bonds. However, because of resonance, the actual bonding in the nitrate ion is a hybrid of these three structures.
To calculate the bond order, we can use the formula:
- Bond Order = (Number of bonding pairs – Number of antibonding pairs) / Number of bonds
In NO3–, there are 4 bonding pairs (since we count each double bond as two and the single bonds as one) and no antibonding pairs. Moreover, we consider that the bonding situation is averaged out across the three resonance forms:
- 4 bonding pairs / 3 bonds = 1.33
Therefore, the bond order reflects the intermediate character of the bonds in the resonance hybrid, indicating that the bonds in NO3– are neither single nor double, but a blend of both, leading us to the conclusion that the bond order is 1.33.