JEE MainChemistryCoordination Compounds
The correct decreasing order of the spin-only magnetic moments of the following complex ions is: (Given Atomic Numbers: Co = 27 , Ni = 28 )
Options
- A[NiCl₄]²⁻ > [CoCl₄]²⁻ > [Ni(CN)₄]²⁻
- B[CoCl₄]²⁻ > [Ni(CN)₄]²⁻ > [NiCl₄]²⁻
- C[Ni(CN)₄]²⁻ > [NiCl₄]²⁻ > [CoCl₄]²⁻
- D[CoCl₄]²⁻ > [NiCl₄]²⁻ > [Ni(CN)₄]²⁻
Correct answer
D. [CoCl₄]²⁻ > [NiCl₄]²⁻ > [Ni(CN)₄]²⁻
Step-by-step solution
For [CoCl₄]²⁻ , the central metal ion is Co²⁺ ( 3d^7 ). Since Cl^- is a weak field ligand and the coordination number is 4, the complex is tetrahedral. The splitting is _t = n(n+2) = 3(5) = 15 BM . For [NiCl₄]²⁻ , the central metal ion is Ni²⁺ ( 3d^8 ). With the weak field ligand Cl^- in a tetrahedral geometry, the configuration is e^4 t₂^4 . The number of unpaired electrons is n = 2 . = 2(4) = 8 BM . For [Ni(CN)₄]²⁻ , the central metal ion is Ni²⁺ ( 3d^8 ). Since CN^- is a strong field ligand, the complex adopts a