Question

Using valence bond theory, deduce the geometry and magnetic nature of [Ni(CN)₄]²⁻.

Answer 1

1. Using valence bond theory (VBT), the complex [Ni(CN)₄]²⁻ can be explained in terms of its geometry and magnetic nature based on the electronic configuration of the metal ion and the type of ligand.
2. In this complex, nickel is in the +2 oxidation state, giving it a 3d⁸ electronic configuration.
3. The ligand cyanide (CN⁻) is a strong field ligand that causes pairing of electrons in the 3d orbitals due to strong crystal field splitting.
4. After pairing, the 3d orbitals contain all paired electrons, and one of the 3d orbitals becomes available for bonding.
5. Nickel then uses one 3d orbital, one 4s orbital, and two 4p orbitals to form dsp² hybrid orbitals.
6. These four hybrid orbitals accept lone pairs from the four cyanide ligands, resulting in a square planar geometry.
7. Because the electron pairing leads to no unpaired electrons in the complex, [Ni(CN)₄]²⁻ is diamagnetic.