Chemistry - Coordination Chemistry Question with Solution | TestHub

In this ligand substitution reaction, the nickel ion remains bonded to six monodentate ligands, meaning the Coordination Number (C.N.) and the number of coordinate bonds remain constant at 6. Since both H₂O and NH₃ are neutral ligands, the Oxidation Number (O.N.) of Nickel does not change and stays as +2. However, the total number of $\sigma$-bonds within the complex ion changes because H₂O has two internal $\sigma$-bonds (O-H) while NH₃ has three (N-H). This increases the total $\sigma$-bond count in the ion from 18 to 24, making options (B) and (C) correct.