Give reason for the statement `[Ni(CN)_(4)]^(2-)` is diamagnetic while `[NiCl_(4)]^(2-)` is paramagnetic in nature .

Explanation

Coordination number of nickel in both the complexes is four and nickel is in +2 oxidation state. It has the electronic configuration

In case of `[Ni(CN)_4]^(2-),CN^(-)` being a strong ligand, the paiiring of electrons takes place and the complex is diamagnetic due to the absence of unpaired electrons.

In case of `[NiCl_4]^(2-), Cl^(-)` being a weak ligand, no pairing of tetrahedral geometry. As there are two unpaired electrons, complex is paramagnetic.