In the change of NO⁺ to NO, the electron is added to

M.O. configuration of NO⁺ is :
$\left(\mathrm{\sigma }1\mathrm{s}{)}^2{\left({\mathrm{\sigma }}^{\ast }1\mathrm{s}\right)}^2\right(\mathrm{\sigma }2\mathrm{s}{)}^2{\left({\mathrm{\sigma }}^{\ast }2\mathrm{s}\right)}^2{\left(\mathrm{\sigma }2{\mathrm{p}}_{\mathrm{z}}\right)}^2{\left(\mathrm{\pi }2{\mathrm{p}}_{\mathrm{x}}\right)}^2{\left(\mathrm{\pi }2{\mathrm{p}}_{\mathrm{y}}\right)}^2$
and M.O. configuration of NO is :
$\left(\mathrm{\sigma }1\mathrm{s}{)}^2\right({\mathrm{\sigma }}^{\ast }1\mathrm{s}{)}^2\left(\mathrm{\sigma }2\mathrm{s}{)}^2\right({\mathrm{\sigma }}^{\ast }2\mathrm{s}{)}^2{\left(\mathrm{\sigma }2{\mathrm{p}}_{\mathrm{z}}\right)}^2{\left(\mathrm{\pi }2{\mathrm{p}}_{\mathrm{x}}\right)}^2{\left(\mathrm{\pi }2{\mathrm{p}}_{\mathrm{y}}\right)}^2{\left({\mathrm{\pi }}^{\ast }2{\mathrm{p}}_{\mathrm{x}}\right)}^1$