Question

Using valence bond theory, explain the hybridisation and magnetic behaviour of the following:

K₂[NiCl₄]

(At. no.: Ni = 28)

Answer 1

The central metal ion in this complex is Ni²⁺, which has an atomic number of 28. Its electronic configuration is [Ar] 3d⁸ 4s⁰. Chloride ions (Cl⁻) are weak-field ligands, so they do not cause pairing of electrons in the d-orbitals. As a result, the 3d electrons in Ni²⁺ remain unpaired. For a complex with four ligands and no pairing, the hybridisation involves one 3d, one 4s, and two 4p orbitals, leading to sp³ hybridisation.

This sp³ hybridisation gives the complex a tetrahedral geometry. Since there are two unpaired electrons in the 3d orbitals, the complex shows paramagnetic behaviour.