Based on Valence Bond Theory, match the complexes listed in Column I with the number of unpaired electrons on the central metal ion, given in Column II No. Complex ions No. Number of unpaired electrons A [FeF₆]³⁻ P 0 B [Fe(CN)₆]⁴⁻ Q 1 C [Fe(H₂O)₆]²⁺ R 5 D [Fe(CN)₆]³⁻ S 4

Step-by-step solution

For [ Fe F ₆ ]³⁻ , the oxidation state of Fe is +3 . The electronic configuration of Fe ³⁺ is [ Ar ] 3d^5 . Since F ⁻ is a weak field ligand, it does not cause pairing. Thus, there are 5 unpaired electrons. This matches (R). For [ Fe ( CN )₆ ]⁴⁻ , the oxidation state of Fe is +2 . The electronic configuration of Fe ²⁺ is [ Ar ] 3d^6 . Since CN ⁻ is a strong field ligand, it causes pairing of electrons in the 3d orbitals. All 6 electrons pair up, resulting in 0 unpaired electrons. This matches (P). For [ Fe ( H ₂ O