If AB₄ molecule is a polar molecule, a possible geometry of AB₄ is

Solution

Chemistry ma’am · 3 steps

Match each shape to its lone pairs; only a lone pair that breaks the symmetry leaves a net dipole.

1. What polar needs. Four identical A–B bond dipoles cancel only when they are arranged symmetrically around A. A polar AB₄ needs a shape where they cannot cancel.

   Geometry	VSEPR type	Example	Dipoles cancel?
   Tetrahedral	AB₄, no lone pair	CH₄	yes, non-polar
   See-saw	AB₄E, 1 lone pair	SF₄	no, polar
   Square pyramidal	AB₅E, 1 lone pair	BrF₅	needs 5 B atoms, not an AB₄ shape
   Square planar	AB₄E₂, 2 lone pairs	XeF₄	yes, non-polar

2. Why see-saw. In see-saw, the lone pair sits in an equatorial position of the trigonal bipyramid. The four bonds are no longer symmetric, so their dipoles add up to a net dipole moment.
3. So. A polar AB₄ molecule can be see-saw, option (b), like SF₄.

The idea to keep. Identical bonds placed symmetrically (tetrahedral, square planar, linear, trigonal planar, octahedral) give zero dipole. A lone pair that spoils the symmetry, as in see-saw, makes it polar.

Answer from the NTA final answer key. Solution by PrepWiser.