Chemistry - Coordination Chemistry Question with Solution | TestHub

The complex having higher number of unpaired electrons will have higher value of spin only magnetic moment. In all these complexes, the central metal ion is in $+2$ oxidation state. ${\mathrm{Zn}}^{2+}$ has $3d^{10}$ outer electronic configuration with 0 unpaired electron. ${\mathrm{Ni}}^{2+}$ has $3d^8$ outer electronic configuration with 2 unpaired electrons. ${\mathrm{Co}}^{2+}$ has $3d^7$ outer electronic configuration with 3 unpaired electrons. ${\mathrm{Mn}}^{2+}$ has $3d^5$ outer electronic configuration with 5 unpaired electrons Hence the correct order of spin-only magnetic moments is $${\left[{\mathrm{MnCl}}_4\right]}^{2-}>{\left[{\mathrm{CoCl}}_4\right]}^{2-}>{\left[{\mathrm{NiCl}}_4\right]}^{2-}>{\left[{\mathrm{ZnCl}}_4\right]}^{2-}\text{. }$$