Question

The hexaaquomanganese (II) ion contains five unpaired electrons while the hexacyano ion contains only one unpaired electron. Explain using Crystal Field Theory.

Answer 1

Mn(II) has an electronic configuration of $3d^{5}4s^0$. In the case of hexaaquomanganese (II) ion the ligand attached to metal is water which is a weak field ligand and is not able to pair up the electrons of 3d subshell and the configuration is $t_2{g}^3$ and $e{g}^2$. whereas in the case of hexacyano ion the $C{N}^{-}$ is a strong field ligand and it causes pairing of electrons in the d orbitals and hence thee exist only one unpaired electron in $t_2{g}^5$$e{g}^0$.