We discussed how to determine whether molecules were polar or not based on their shapes. To be polar, a molecule has to

1. have at least one polar bond.
2. be shaped in such a way that all of the molecule’s polar bonds don’t cancel each other out.

Dichloromethane, CH₂Cl₂, might appear to be a nonpolar molecule at first glance. Depending on how we draw the Lewis structure, we might fool ourselves into thinking that the two C-Cl polar bonds in the molecule would cancel each other out. However, that’s not really the case. The chlorine bonds are not arranged in a way that allows them to cancel.

This rendering is arranged in the way we draw the molecule on our paper. The hydrogen and carbon atoms are in the plane of the screen, and the chlorine atoms are in front of and behind the screen. You can see that the molecule has a “chlorine side” and a “hydrogen side”, and thus is polar.

If you can’t see it, this rotated rendering below makes the “sides” more obvious.