Answer:
Square planar
Explanation:
Ni^2+ is a d8 ion. It could exist in either a square planar or a tetrahedral geometry depending on the identity of the ligand. However, strong field ligands often lead to a square planar geometry owing to a greater crystal field splitting.
From the splitting diagrams of nickel II ion in tetrahedral and square planar geometries, it can easily be seen that a diamagnetic complex only arises from the square planar geometry.
Note that both tetrahedral and square planar geometries involve a coordination number of four.
