So either two opposite, two positive charges or two negative charges. In both of these cases, the electrostatic force is repulsive in nature. And so, in this case, the two atoms will tend to move apart from one another. So unlike gravity, unlike the gravitational force, the electric force that essentially holds and allows the interaction between atoms and molecules is both attractive and, in some cases, repulsive in nature, depending on the type of charges that are found in close proximity. And all the different types of bonds we're going to discuss in this lecture are electric in nature. So we have two categories of bonds.