# Q.20. Which of the following is a polar molecule? (1) $S{F}_{4}$ (2) $Si{F}_{4}$ (3) $Xe{F}_{4}$ (4) $B{F}_{3}$

Dear student,
SiF4 and BF3 have regular tetrahedral and trigonal planar shape respectively and all regular structures have zero dipole moment. In XeF4 it has square planar geometry which also makes it having a zero dipole moment. In SF4 the molecule is having see-saw geometry since sulphur has 4 electrons bonded to 4 Fluorine atoms and has a lone pair left thereby making it sp3d hybridized which is not a regular structure since equatorial Fluorine cannot cancel the moment generated by lone pair and therefore SF4 is a polar molecule.

Hence answer is (1)

Hope it helps
Regards

• 16
BF3
• -7
BF3
• -2
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