Question

Using Crystal Field theory, write the number of unpaired electrons in octahedral complexes of Fe³⁺ in the presence of:
(I) Strong field ligand
(II) Weak field ligand
Atomic number: Fe = 26

Answer 1

For Fe³⁺ (d⁵ configuration), the number of unpaired electrons depends on the ligand field strength.

(I) With a strong field ligand, the d-orbitals split, causing pairing of electrons. Thus, Fe³⁺ in the presence of a strong field ligand will have 0 unpaired electrons.

(II) With a weak field ligand, the d-orbitals do not split enough to cause electron pairing. Therefore, Fe³⁺ in the presence of a weak field ligand will have 5 unpaired electrons.