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The correct order of the calculated spin-only magnetic moments of complexes (A) to (D) is : (A) Ni(CO)4 (B) [Ni(H2O)6]Cl2 (C) Na2[Ni(CN)4] (D) PdCl2(PPh3)2

1. (C) ≈ (D) < (B) < (A)
2. (A) ≈ (C) < (B) ≈ (D)
3. (A) ≈ (C) = (D) < (B)
4. (C) < (D) < (B) < (A)

Correct answer: (C) ≈ (D) < (B) < (A)

Solution

The correct order reflects the number of unpaired electrons in each complex, which determines the spin-only magnetic moment. Ni(CO)4 and Na2[Ni(CN)4] are low-spin complexes with no unpaired electrons, resulting in similar low magnetic moments, while [Ni(H2O)6]Cl2 has unpaired electrons due to weaker field ligands, leading to a higher magnetic moment. PdCl2(PPh3)2 also has unpaired electrons but less than [Ni(H2O)6]Cl2, thus placing it in the order.

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