Question -
Answer -
Cr isin the +3 oxidation state i.e., d3 configuration.Also, NH3 is a weak field ligand that does notcause the pairing of the electrons in the 3d orbital.
Cr3+
Therefore,it undergoes d2sp3 hybridizationand the electrons in the 3d orbitals remain unpaired. Hence, it isparamagnetic in nature.
In[Ni(CN)4]2−, Ni exists in the +2oxidation state i.e., d8 configuration.
Ni2+:
CN− isa strong field ligand. It causes the pairing of the 3d orbitalelectrons. Then, Ni2+ undergoes dsp2 hybridization.
As there are nounpaired electrons, it is diamagnetic.