`[Fe(H_(2)O)_(6)]^(3+)` is strongly paramagnetic whereas `[Fe(CN)_(6)]^(3-)` is weakly paramagnetic Explain.

Explanation

Outer configuration of `""_(26)Fe=3d^(6)4s^(2)`. In both the complex Fe is present as `Fe^(3+)` ion.

In the presence of `CN^(-)` (a strong field ligand) the 3d-electrons pair up leaving only one unpaired electron. The hybridization is `d^(2)sp^(3)` forming an inner orbital complex.

In the presence of `H_(2)O`, (a weak field ligand), 3d-electrons do not pair up. The hybridization is `sp^(3)d^(2)` forming an outer orbital complex containing five unpaired electrons. Hence, it is strongly paramagnetic.