Take a look at the periodic table. On the left hand side are metals, in dark blue, and they take up a big chunk of the table. On the far right, in light blue, are the nonmetals. We’ve now seen what happens when we combine a metal (sodium) with a nonmetal (chlorine)—an ionic bond. And this is generally the case—combining a metal with a nonmetal generally creates a salt—a substance held together by electrostatic attractions between ions. On the other hand, combining nonmetals with nonmetals usually creates compounds held together by covalent bonds. (Note that hydrogen can be treated as a metal or as a nonmetal).

There are several other types of chemical bonds, all of them weaker than ionic or covalent bonds. But the only one we really need to talk about now is a special kind of electrostatic bonding called a hydrogen bond. Hydrogen bonding, as we’ll see in future issues, is extremely important in biological systems. In order to understand hydrogen bonding, we need to finally discard our quaint illusions about subatomic particles like electrons. It’s time to look at a more sophisticated (if not more "real") version of the atom.