Chemistry - PERIODIC TABLE Question with Solution | TestHub

Higher ionisation energy of ${\mathrm{N}}_2$ as compared to atomic N is because the electron is removed from a bonding HOMO in ${\mathrm{N}}_2$.

Low ionisation energy of NO as compared to atomic N is because the electron is removed from an antibonding HOMO, which is higher in energy than the parent atomic orbitals.

Formation of ${\mathrm{NO}}^{+}$increases bond order compared to NO , and ${\mathrm{NO}}^{+}$becomes isosteric with ${\mathrm{N}}_2$.

Since NO contains one electron more than ${\mathrm{N}}_2$, the HOMO of NO must be a bonding MO , hence $\mathrm{IE}(\mathrm{NO})>\mathrm{IE}\left({\mathrm{N}}_2\right)$.