When two or more atoms join together, they form a molecule. There are two basic types of molecules: elements and
compounds.

Here is one way to construct models of each of the two types of molecule:

a. Element.

Get four medium-sized styrofoam balls. (Each ball represents a carbon atom.) Join the styrofoam balls
together with 2-inch lengths of heavy wire.

When four carbon atoms join together in this way, they form one molecule of carbon.

b. Compound.

Salt is made up of two different kinds of atoms: one sodium atom and one chlorine atom joined side by side make one molecule of salt. Construct a model of a salt
molecule using styrofoam balls (a small one for sodium and a large one for chlorine).

Put the balls together with wire so 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).

The molecular structure of compounds is made up of more than one kind of atom.

(Compare the models for similarities and differences.)

From the comparisons you will find that some models are made up of atoms that are all the same kind (elements), while others are made up of different kinds of atoms (compounds).