What may be the geometry of molecule if ${\mathrm{AX}}_3$ molecule has non-zero dipole moment.

If an AX₃ molecule has a non-zero dipole moment (μ ≠ 0), its geometry cannot be symmetrical (like trigonal planar), because in symmetrical geometries, the bond dipoles cancel out, resulting in a net dipole moment of zero.

Correct Answer:

If an AX₃ molecule has a non-zero dipole moment, its geometry is most likely trigonal pyramidal.

Reason:

In trigonal planar geometry (e.g., BF₃), the three X atoms are arranged symmetrically around the central atom A in one plane. The individual bond dipoles cancel out → μ = 0.

But in trigonal pyramidal geometry (e.g., NH₃), the molecule has a lone pair on A, which distorts the shape, making it asymmetrical, so the bond dipoles do not cancel → μ ≠ 0

Example:

NH₃ (Ammonia) is AX₃ and has a trigonal pyramidal shape → μ ≠ 0