Question

Which of the following species have undistorted octahedral structures?
1.$S{F}_6$ 2.$P{F}_6^{-}$
3.$Si{F}_6^{2-}$ 4.$Se{F}_6$
Select the correct answer using the codes given below.

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

Answer 1

Answer: (D)

$1,2$ and $4$

In $S{F}_6$, sulphur has 12 electron around the central atom, this means that there are 6 pairs of electrons arranged in octahedral shape with bond angle ${90}^0$ in F-S-F.

In $Se{F}_6$, the central Se atom is bonded with 6 fluorine atom with 6 pairs of electron arranged in octahedral shape.

Phosphorus belongs to group 5 so it has 5 electron in valence shell. In $P{F}_6^{-}$, phosphorus is surrounded by 6 fluorine atoms which contribute 6 electron to valence shell, hence, the total become 11 electrons along with one negative charge on phosphorous atom. So, with total 12 electron, according to VSEPR $P{F}_6^{-}$ shows undistorted octahedral structures.