Question

Hexaflouroferrate(III) ion is an outer orbital complex. the number of unpaired electrons are:

• A. 1
• B. 5
• C. 4
• D. Unpredictable

Answer 1

The correct option is B 5

Outer orbital complexes are coordination compounds composed of a central metal atom having hybridization of the atomic orbitals including s, p and d orbitals from the outermost shell.
Hexafluroferrate(III) ion $\left(\right[Fe{F}_6{]}^{3+})$
Electronic configuration of $Fe:\left[Ar\right]4s^{2}3d^6$
Here $Fe$ shows oxidation state of +3
Thus its electronic configuration can be given as $\left[Ar\right]3d^5$

Thus, it has 5 unpaired electrons.
The electron pair donate by $F$ enters into $4s,4p$ and two $4d$ subshell to form $s{p}^3{d}^2$ hybrid orbital.