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

Explanation

Mn in +2 state has the configuration `3d^(5)`. In presence of `H_(2)O)` as weak ligand pairing does not take place. Distribution of these five electrons is `t_(2g)^(3)e_(g)^(2)`, i.e., all the electrons remain unpafred. In presence of `CN^(-)` as strong ligand, the distribution is `t_(2g)^(5)e_(g)^(0)`, because of pairing and hence two `t_(2g)` orbitals contain paired electrons while the third `t_(2g)` orbital contains one unpaired electron.