Polarity of Molecules

[604633468]

After doing a few questions, I've been confused on the relation between electron pair geometry, lone pairs and the polarity of a molecule. The first step to determining polarity would be to find a non-symmetric electron pair geometry. However if the shape is symmetric and there is a lone pair involved there would be an implied polarity. So does this mean any existence of a lone pair can cause polarity?

[kshalbi]

Any existence of a lone pair does cause polarity as long as there is not another lone pair to cancel out the dipole moment. The lone pairs cancel each other out if they are on the same plane and there is no bonding electrons on the same plane as the lone pairs.

[ConnieDo3I]

I'm not completely sure, but if there's a lone pair, I don't think the molecule would be symmetric. I guess, then, you could infer that molecules with lone pairs are polar. (I have yet to find an example to prove otherwise.)

[Regarding polarity in general: It might help to draw out the structure of the molecule and draw arrows pointing in the direction of the electron pulls. If the arrows cancel out, then the molecule is nonpolar. If not, then it's polar. (But keep in mind the magnitudes of the pulls differ among types of bonds and types of atoms attached to bonds)]

Sorry for the incomplete/vague answer, but this is what I think. Hope it helps!