Question

Which of the following would have a permanent dipole moment?

• A. $B{F}_3$
• B. $S{F}_4$
• C. $Si{F}_4$
• D. $Xe{F}_4$

Answer 1

The correct option is B $S{F}_4$

Permanent dipole moment :

A: $B{F}_3$

(Image 1)

In $B{F}_3$, the dipole moments cancel each other. Hence it does not have a permanent dipole moment.

B.$S{F}_4$

(Image 2)

The hybridization of a $S{F}_4$ molecule is $s{p}^{3}d$, thus a seesaw structure (bent because of lp-lp repulsion) and thus having a net dipole moment.

C.$Si{F}_4$

(Image 3)

In $Si{F}_4$ the dipole moments cancel each other. Hence it does not have a permanent dipole moment.

D. $Xe{F}_4$-has a planar structure, so it is non-polar

(Image 4)

Hence the correct option is B - $S{F}_4$ - has a permanent dipole.