Polar vs nonpolar

[KarenaKaing_1D]

Are there any general rules to tell if a structure is polar or nonpolar? For instance, trigonal planar molecules are nonpolar if all three molecules are the same.

[Nikhil Davuluri 2A]

Polarity comes when molecules have a net dipole moment in any direction. Therefore, if a central atom is bonded to multiple elements which are different, the dipole moments will most likely not cancel. This will result in a polar molecule - one part of it will have a partial negative charge while another will have a partial positive charge. Also, a molecule will be polar if the central atom has lone pairs.
Hope this helps.

[Vonny Chong]

In general the only possible shapes that can be nonpolar are: linear, trigonal planar, tetrahedral, trigonal bipyramidal, octahedral and square planar, IF all the attached atoms are the same. If there are lone pairs or one or more different attached atoms, the structure is very likely to be polar.

[Chem_Mod]

Nice answers, gang.