Answer: Pt2+ (5d8) has larger CFSE favouring square planar; Ni2+ (3d8) has smaller Delta and the pairing energy penalty for square planar is not compensated.
- A Pt2+ (5d8) has larger CFSE favouring square planar; Ni2+ (3d8) has smaller Delta and the pairing energy penalty for square planar is not compensated
- B Platinum's much greater atomic mass relative to nickel is what forces the square planar shape on its own as frequently described in most textbook accounts
- C The chloride ligand bound to nickel is somehow physically larger than the same chloride ligand bound to platinum during normal conditions as generally observed
- D Nickel is supplied with extra coordinating chloride ligands in solution that platinum is largely denied access to in typical laboratory settings
Correct answer: A. Pt2+ (5d8) has larger CFSE favouring square planar; Ni2+ (3d8) has smaller Delta and the pairing energy penalty for square planar is not compensated
Explanation: Square planar (d8) requires a large crystal field splitting. 5d orbitals of Pt2+ are larger and interact more strongly with ligands, giving large Delta favouring square planar. 3d Ni2+ with Cl- (weak field) favours tetrahedral.
The three common coordination geometries: octahedral (6 ligands), tetrahedral (4 ligands), and square planar (4 ligands in one plane).
Concept context
Study of compounds where a central metal atom is bonded to surrounding ligands. Covers nomenclature, types of isomerism, bonding theories (VBT, CFT), and applications in medicine, photography, and industry.