We will build some models of a compound. First, what is a compound? Mr. Webster tells us that a compound is something made of more than one element (ingredient). What do we see every day that is a compound? Almost everything!

Salt is a compound. It is made of two different kinds of atoms: one sodium atom and one chlorine atom. Joined side by side, these two atoms make one molecule of salt.

That brings another question: What is a molecule? It is what we have when two or more atoms join together.

Here we go on our project! Look at a small grain of salt under a hand lens or a microscope, and examine its' shape carefully. Salt actually comes in several different kinds of shapes. Refined salt, commonly called "table salt," is fairly regular in shape, because it has been through several machines before it was packaged, and in order to make it easy to pour or shake, the grains are sort of rounded. Then there is rock salt, which is in irregular chunks. We could hit a couple chunks of rock salt with a hammer, and get a more natural shape of granule. Kosher salt is sea salt, and the grains are somewhat squared. In any case, the shapes of salt grains, or any other grains, are interesting when viewed under magnification.

Construct several models of a salt molecule, using one small and one large styrofoam ball. (The small styrofoam ball represents a sodium atom and the large one a chlorine atom.)

Fasten the balls together with wire in such a way that a sodium and a chlorine atom are always side by side -- up and down, in front and in back of each other. (The molecules will always form a cube).

Compare the shape of the model with the small grains of salt you observed earlier.

The molecular structure of compounds is composed of more than one kind of atom, and the possible combinations of different atoms are almost limitless.