`[Fe(H_2O)_6]^(3+)` is strongly paramagnetic whereas `[Fe(CN)_6]^(3-)` is weakly paramagnetic. Explain.

Explanation

In both the complexes `Fe` is in `+2` state with the configuration `3d^(6)`, i.e., it has four unpaired electrons. In presence of the weak `H_2O` ligand, they do not pair up. In presence of strong `CN^(ɵ)` ligand, they pair up leaving no unpaired electron. Because of the difference in the number of unpaired electrons, they have different colours.