In which of the following pairs, the outermost electronic...

Option 1: ${Mn}^{+ 2}\left[Ar\right]3{d}^{5}, {Cr}^{+}\left[Ar\right]3{d}^{5}$

Cr is expected to have the highest second ionization enthalpy as after removal of 4s electrons, the electrons will be removed from d-orbital. Cr+ have stable half-filled d-orbital with maximum spin multiplicity.

Option $- 2{Ni}^{+ 2}\left[Ar\right]3{d}^{8}, {Cu}^{+}\left[Ar\right]3{d}^{10}$

Option $- 3{Fe}^{+ 2}\left[Ar\right]3{d}^{6}, {Co}^{+}\left[Ar\right]3{d}^{7}4{s}^{1}$

Option $- 4{V}^{+ 2}\left[Ar\right]3{d}^{3}, {Cr}^{+}\left[Ar\right]3{d}^{5}$