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

Explanation

Mn in `+2` oxidation state has the electronic configuration `(3d^(5)4s^(0))`. In presence of `H_(2)O` (weak ligand) as ligand, the distribution of five d - electrons is `t_(2)^(3)e_(g)^(2)` i.e., all five electrons remain unpaired. On the other hand, in presence of `CN^(-)` ion (strong ligand, which cause crystal field splitting to a large extent) as ligand, the distribution of five d - electrons is `t_(2g)^(5)e_(g)^(0)` i.e., two `t_(2g)` orbitals contain paired electrons, while the third `t_(2g)` orbital contains one unpaired electron.