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

The count of unpaired electrons for Fe³⁺ (d⁵ configuration) is contingent upon the strength of the ligand field.

(I) In the presence of a strong field ligand, d-orbital splitting occurs, leading to electron pairing. Consequently, Fe³⁺ with a strong field ligand will exhibit 0 unpaired electrons.

(II) With a weak field ligand, insufficient d-orbital splitting prevents electron pairing. Therefore, Fe³⁺ in the presence of a weak field ligand will possess 5 unpaired electrons.