Which among the following is diamagnetic?

Step-by-step solution

In [ Ni ( CN )₄ ]²⁻ , the oxidation state of Ni is +2 . The electronic configuration of Ni ²⁺ is [ Ar ] 3d^8 . Since CN ⁻ is a strong field ligand, it causes pairing of electrons in the 3d orbitals. The configuration becomes t_ 2g ^6 e_g^2 (or d_ xy ^2 d_ yz ^2 d_ zx ^2 d_ z^2 ^2 d_ x^2-y^2 ^0 ), resulting in zero unpaired electrons, making it diamagnetic. In [ Fe ( CN )₆ ]³⁻ , Fe is in +3 state ( 3d^5 ). With a strong field ligand, it has one unpaired electron, making it paramagnetic. In [ Co ( F )₆ ]³⁻ , Co is in