Question

For the complex ion, [Fe(CN)₆]³⁻:

Show the hybridisation diagrammatically.

Answer 1

In [Fe(CN)₆]³⁻, iron is in the +3 oxidation state, with the configuration [Ar] 3d⁵. The ligand CN⁻ is a strong field ligand, which causes pairing of electrons in the 3d orbitals. This allows Fe³⁺ to use two 3d, one 4s, and three 4p orbitals for d²sp³ hybridisation. 

The hybridisation of the central metal ion in Fe(CN)₆]³⁻ is d²sp³.