Answer: [Ni(CN)4]2-.
- A [CoF6]3-
- B [Fe(H2O)6]2+
- C [NiCl4]2-
- D [Ni(CN)4]2-
Correct answer: D. [Ni(CN)4]2-
Explanation: [Ni(CN)4]2- is square planar (dsp2) with Ni(II) d8 fully paired, so it is diamagnetic; the other three have unpaired electrons.
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.