Question

Find bond order; N2 +, N2 - , N2 +2, CO. Arrange the given molecules in increasing order of their acidic strength.

Answer 1

To determine the bond order of each molecule, we need to examine the molecular orbital diagram for each species. The bond order is calculated by taking the difference between the number of bonding electrons and the number of antibonding electrons and dividing it by 2.

N₂⁺:
In N₂⁺, one electron is removed from the antibonding \( \pi^*_{2p} \) orbital. The molecular orbital configuration is then: 
- Bonding electrons: 5 
- Antibonding electrons: 2
The bond order is calculated as: \[ \text{Bond order} = \frac{5 - 2}{2} = 1.5 \] So, the bond order for N₂⁺ is 1.5.

N₂^-:
In N₂^-, an additional electron is added to the antibonding \( \pi^*_{2p} \) orbital. The molecular orbital configuration is: 
- Bonding electrons: 5 
- Antibonding electrons: 4
The bond order is: \[ \text{Bond order} = \frac{5 - 4}{2} = 0.5 \] Therefore, the bond order for N₂^- is 0.5.

N₂²⁺:
N₂²⁺ does not exist as a stable molecule. This is because it requires the addition of four electrons to the antibonding orbitals, which is highly unfavorable in terms of molecular stability.

CO:
CO has a triple bond between carbon and oxygen. The molecular orbital diagram for CO shows that there are 10 bonding electrons and 6 antibonding electrons. The bond order is: \[ \text{Bond order} = \frac{10 - 6}{2} = 2 \] So, the bond order for CO is 2.

Arranging the molecules in increasing order of their acidic strength:
The increasing order of acidic strength can be determined by looking at the bond order and stability. A higher bond order typically corresponds to greater stability and weaker acidity (less likely to donate protons). Therefore, the order is:

N₂^- < N₂⁺ < CO < N₂²⁺

Conclusion:
In terms of increasing acidic strength, the correct order is: N₂^-, N₂⁺, CO, N₂²⁺.