Question

State the hybridization and magnetic property of [Fe(CN)₆]³⁻ ion according to the valence bond theory.

Answer 1

1. In the complex ion [Fe(CN)₆]³⁻, the oxidation state of iron is +3. 
2. The electronic configuration of Fe is [Ar] 3d⁶ 4s², and that of Fe³⁺ is [Ar] 3d⁵.
3. The ligand CN⁻ is a strong field ligand and causes pairing of 3d electrons.
4. After pairing, five electrons occupy the 3d orbitals, leaving one 3d orbital vacant.
5. The metal ion undergoes d²sp³ hybridisation using two 3d, one 4s and three 4p orbitals.
6. This leads to an octahedral geometry for the complex.
7. As one unpaired electron remains, the complex is paramagnetic in nature.