Question

Hexafluoroferrate (III) ion is an outer orbital complex. The number of unpaired electrons present in Fe is

• A. 1
• B. 5
• C. 4
• D. None of these

Answer 1

The correct option is B

5

We know that $F{e}^{3+}$ will have an electronic configuration of $3d^5$. Depending on whether the ligand that attacks this is weak or strong field, it may or may not cause pairing of electrons. That is the key idea that will help us solve this question.
Since $F^{-}$ is a weak field ligand, it will not cause any pairing of electrons.
Due to Hund's rule, each d-orbital of iron will have one electron resulting in 5 unpaired electrons
$\therefore [Fe{F}_6{]}^{3-}$ is $s{p}^3{d}^2$ hybridized since it is already given that this is an outer orbital complex.