Question

Which of the following species have undistorted octahedral structures?
1. $S{F}_6$
2. $P{F}_6^{-}$
3. $Si{F}_6^{2-}$
4. $Xe{F}_6$

• A. $2,3$ and $4$
• B. $1,3$ and $4$
• C. $2$ and $3$
• D. $1,2$ and $3$

Answer 1

The correct option is D $1,2$ and $3$

$H=\frac{1}{2}[V+M-C+A]$
where,
H= Number of orbitals involved in hybridization.
V=Valence electrons of a central atom.
M- Number of monovalent atoms linked to the central atom.
C= Charge of the cation.
A= Charge of the anion.
Consider the hybridization and shape of the options:-
1) $S{F}_6$
$H=\frac{1}{2}[6+6]=6$.
$\Rightarrow s{p}^3{d}^2$ hybridized state.
Octahedral in shape.
2) $P{F}_6^{-}$
$H=\frac{1}{2}[5+6+1]=6$.
$\Rightarrow s{p}^3{d}^2$ hybridized state.
Octahedral in shape.
3) $Si{F}_6^{2-}$
$H=\frac{1}{2}[4+6+2]=6$.
$\Rightarrow s{p}^3{d}^2$ hybridized state.
Octahedral in shape.
4) $Xe{F}_6$
$H=\frac{1}{2}[8+6]=7$.
$\Rightarrow s{p}^3{d}^3$ hybridized state.
Distorted Octahedron in shape.
Hence option D is the right answer.