Why hexaquamanganese(II)ion contains five unpaired electrons, while the hexacyno manganese (II)ion contains only one unpaired electron ?

Explanation

`H_(2)O` is a weak field ligand and CN is a strong field ligand. Thus in `[Mn(H_(2)O)_(6)]^(2+)` pairing of unpaired electrons is not possible and it possesses five unpaired electrons. In `[Mn(CN)_(6)]^(4-)` pairing of four unpaired electrons takes place and it possesses one unpaired electron.