Question

Give the number of unpaired electrons in the following complex ions: 

(i) [FeF₆]^-4

(ii) [Fe(CN)₆]^-4

Answer 1

(i) In [FeF₆]^-4, Fe is in +2 oxidation state. It has d⁶ configuration. As F^– is a weak ligand, the electrons in 3d orbital are not paired.

i-e.,

Hence, it has 4 unpaired electrons.

(ii) In [Fe(CN)₆]^-4 also, Fe is in +2 oxidation state and it has d⁶ configuration. Because CN^– ion is a strong ligand, the electrons in 3d orbital of Fe⁺² are paired and so there are no unpaired electrons.