Answer: Low spin: CN- is strong field, large Delta causes maximum pairing (t 2g 6 eg1, 1 unpaired).
- A Low spin: CN- is strong field, large Delta causes maximum pairing (t<sub>2g</sub><sup>6</sup> eg1, 1 unpaired)
- B High spin with three unpaired electrons distributed across t<sub>2g</sub> and eg in the majority of cases studied
- C Largely diamagnetic with zero unpaired electrons in this d7 ion as widely reported
- D High spin with five unpaired electrons, the maximum possible for d7 in standard practice
Correct answer: A. Low spin: CN- is strong field, large Delta causes maximum pairing (t<sub>2g</sub><sup>6</sup> eg1, 1 unpaired)
Explanation: Co2+ (d7) with strong field CN-: low spin configuration is t<sub>2g</sub><sup>6</sup> eg1 with only 1 unpaired electron (mu ≈ 1.73 BM).
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.