AP BIOLOGY

Detailed explanation-1: -Molecules in which all of the atoms surrounding the central atom are the same tend to be nonpolar if there are no lone pairs on the central atom. If some of the atoms surrounding the central atom are different, however, the molecule may be polar.

Detailed explanation-2: -A polar molecule always contains polar bonds, but some molecules with polar bonds are nonpolar.

Detailed explanation-3: -Lone pairs occupy a region of electron density, and therefore change the shape of the molecule and the placement of atoms surrounding the central atom. This can cause molecules to no longer be symmetrical and increase the polarity of the molecules.