Question -
Answer -
Ni isin the +2 oxidation state i.e., in d8 configuration.
Thereare 4 CN− ions. Thus, it can either have atetrahedral geometry or square planar geometry. Since CN− ionis a strong field ligand, it causes the pairing of unpaired 3d electrons.
Itnow undergoes dsp2 hybridization. Since all electrons arepaired, it is diamagnetic.
Incase of [NiCl4]2−, Cl− ionis a weak field ligand. Therefore, it does not lead to the pairing of unpaired3d electrons. Therefore, it undergoes sp3 hybridization.
Since there are 2unpaired electrons in this case, it is paramagnetic in nature.