In which of the following processes, the bond order increases and paramagnetic character changes to diamagnetic one?

We need to find the process where the bond order increases AND the paramagnetic character changes to diamagnetic.

Option A: $$\text{O}_2 \to \text{O}_2^+$$

$$\text{O}_2$$: Bond order = 2, paramagnetic (2 unpaired electrons).

$$\text{O}_2^+$$: Bond order = 2.5, paramagnetic (1 unpaired electron).

Bond order increases but remains paramagnetic. Does not satisfy both conditions.

Option B: $$\text{O}_2 \to \text{O}_2^{2-}$$

$$\text{O}_2$$: Bond order = 2, paramagnetic.

$$\text{O}_2^{2-}$$: Bond order = 1, diamagnetic.

Bond order decreases. Does not satisfy.

Option C: $$\text{NO} \to \text{NO}^+$$

$$\text{NO}$$: Bond order = 2.5, paramagnetic (1 unpaired electron in $$\pi^*_{2p}$$).

$$\text{NO}^+$$: Bond order = 3, diamagnetic (the unpaired antibonding electron is removed).

Bond order increases (2.5 $$\to$$ 3) and paramagnetic $$\to$$ diamagnetic. Both conditions satisfied.

Option D: $$\text{N}_2 \to \text{N}_2^+$$

$$\text{N}_2$$: Bond order = 3, diamagnetic.

$$\text{N}_2^+$$: Bond order = 2.5, paramagnetic (1 unpaired electron).

Bond order decreases and diamagnetic $$\to$$ paramagnetic. Opposite of required.

The correct answer is Option C: $$\text{NO} \to \text{NO}^+$$.