Question

Choose the correct statement for the [Ni(CN)4]²⁻ complex ion (Atomic no. of Ni = 28)

• A. The complex is square planar and paramagnetic.
• B. The complex is tetrahedral and diamagnetic.
• C. The complex is square and diamagnetic.
• D. The complex is tetrahedral and paramagnetic.

Answer 1

The Correct Option is C

• Nickel's electronic configuration: Ni has an atomic number of 28, so its electronic configuration is [Ar]3d⁸4s². In [Ni(CN)₄]^2-, Ni is in the +2 oxidation state (Ni²⁺), with an electronic configuration of [Ar]3d⁸.
• CN^- as a strong-field ligand: Cyanide (CN^-) is a strong-field ligand. This means it causes a large splitting of the d-orbitals.
• Square planar geometry: Strong-field ligands like CN^- favor square planar geometry for d⁸ ions. This is because the large splitting energy stabilizes the square planar arrangement.
• Diamagnetic nature: In a square planar complex with a strong field ligand, the d-orbitals split such that all 8 d-electrons pair up in the lower energy orbitals. Because all electrons are paired, the complex is diamagnetic. There are no unpaired electrons.

Therefore, the complex is square planar and diamagnetic.

Correct Answer: The complex is square planar and diamagnetic.