Arrange the complex ions in the increasing order of their magnetic moments A. [ Fe ( H ₂ O )₆ ]²⁺ B. [ Fe ( CN )₆ ]⁴⁻ C. [ Fe ( CN )₆ ]³⁻ D. [ FeF ₆ ]³⁻

Step-by-step solution

The magnetic moment is calculated using the formula = n(n+2) B.M., where n is the number of unpaired electrons. A. In [ Fe ( H ₂ O )₆ ]²⁺ , Fe is in +2 oxidation state ( 3d^6 ). H ₂ O is a weak field ligand, so electrons remain unpaired: t_ 2g ^4 e_g^2 . Number of unpaired electrons n = 4 . = 4(4+2) = 24 4.90 B.M. B. In [ Fe ( CN )₆ ]⁴⁻ , Fe is in +2 oxidation state ( 3d^6 ). CN ⁻ is a strong field ligand, causing pairing: t_ 2g ^6 e_g^0 . Number of unpaired electrons n = 0 . = 0 B.M. C. In [ Fe ( CN )₆ ]³⁻ , Fe is