How can a molecule be nonpolar when it consists of atoms that have different electronegativities?

You must calculate the EN larger number subtracted by the smaller number, and also draw it too.

Then you have to look at a scale;

Non-polar: 0-0.5

Polar Covalent: 0.6-1.6

Ionic: 1.7+

If you draw the molecule and they are symmetrical it will be non-polar but with polar bonds if you calculate the EN.