Which of the following species is iso-electronic with $\mathrm{Cr}?$

The correct order for the increasing ionization enthalpies for the following is:

$\left(\mathrm{i}\right) 1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^2$
$\left(\mathrm{ii}\right) 1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^1$
$\left(\mathrm{iii}\right) 1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^6$
$\left(\mathrm{iv}\right) 1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^2$
$\left(\mathrm{v}\right) 1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^1$