10.
Explain on the basis of valence bond theory that [Ni(CN)4]2– ion with square planar is diamagnetic and the [NiCl4]2– ion with tetrahedral geometry is paramagnetic.
(i) [Ni(CN)4]2–
Ni is in the +2 oxidation state i.e., in d
8 configuration.
There are 4 CN− ions. Thus, it can either have a tetrahedral geometry or square planar geometry. Since CN− ion is a strong field ligand, it causes the pairing of unpaired 3d electrons.
CN– will cause pairing of electrons. It is diamagnetic in nature due to the unpaired electron.
(ii) [Ni(Cl4)]2–
In case of [NiCl4]
2−, Cl
− ion is a weak field ligand. Therefore, it does not lead to the pairing of unpaired 3d electrons. Therefore, it undergoes sp3 hybridization. Since there are 2 unpaired electrons in this case, it is paramagnetic in nature.
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