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

Let's analyze each option: <br/><br/> Option A: $\mathrm{O}_{2} \rightarrow \mathrm{O}_{2}^{2-}$<br/><br/> The bond order of $\mathrm{O}_{2}$ is 2 and it is paramagnetic. When two electrons are added to form $\mathrm{O}_{2}^{2-}$, the bond order becomes 1 (decreases) and it becomes diamagnetic. This option does not meet the required conditions. <br/><br/> Option B: $\mathrm{N}_{2} \rightarrow \mathrm{N}_{2}^{+}$<br/><br/> The bond order of $\mathrm{N}_{2}$ is 3 and it is diamagnetic. When one electron is removed to form $\mathrm{N}_{2}^{+}$, the bond order becomes 2.5 (decreases) and it remains diamagnetic. This option does not meet the required conditions. <br/><br/> Option C: $\mathrm{NO} \rightarrow \mathrm{NO}^{+}$<br/><br/> The bond order of $\mathrm{NO}$ is 2.5 and it is paramagnetic. When one electron is removed to form $\mathrm{NO}^{+}$, the bond order becomes 3 (increases) and it becomes diamagnetic. This option meets the required conditions. <br/><br/> Option D: $\mathrm{O}_{2} \rightarrow \mathrm{O}_{2}^{+}$<br/><br/> The bond order of $\mathrm{O}_{2}$ is 2 and it is paramagnetic. When one electron is removed to form $\mathrm{O}_{2}^{+}$, the bond order becomes 2.5 (increases) and it remains paramagnetic. This option does not meet the required conditions. <br/><br/> Therefore, the correct answer is $\mathrm{NO} \rightarrow \mathrm{NO}^{+}$.