`[Fe(CN)_(6)]^(4-)` and `[Fe(H_(2)O)_(6)]^(2+)` are of different colours in dilute solutions why?

Explanation

In both the complexes, Fe is in +2 state with the configuration `3d^(6)`, i.e., it has four unpaired electrons. As the ligands `H_(2)O` and `CN^(-)` possess different crystal field splitting energy `(Delta_(0))`, they absorb different components of the visible light (VIBGYOR) for d - d transition. Hence, the transmitted colours are different.