The electrons in a covalent bond are shared evenly when they are bonding two atoms of the same element. When they are shared between atoms of different elements, however, one of those atoms may have a greater pull on those electrons. The result is a dipole. Duration: 7:11.
The polarity of a bond between two atoms can be deduced by looking at the relative positions of the two atoms in the periodic table. In general, the farther apart they are, the greater the polarity. Duration: 5:56.
Determining whether a molecule is polar or nonpolar requires a careful study of the geometry of the molecule. In some instances, would-be dipoles balance each other out to make the molecule, as a whole, nonpolar. Duration: 7:04.