What makes a molecule nonpolar?

Two ways to have no net dipole

Equal sharing: the atoms in N₂ are identical, so the bond has no permanent dipole. Cancellation: each C=O bond in CO₂ is polar, but its linear structure places two equal dipoles in opposite directions.

Shape matters more than a quick count of polar bonds. A symmetric molecule such as SF₆ can be nonpolar even though every S–F bond is polar.