Most kinds of matter are compounds – they are formed when elements join together. Just as the tiniest bit of an element is called an atom, the tiniest bit of a compound is called a molecule. A molecule is a group of joined atoms.
Molecules can be very simple. When you breathe air, your body takes in molecules of a gas called oxygen. Each oxygen molecule is made up of two oxygen atoms joined together.
But some molecules have many kinds of atoms. The “vinegary” taste of vinegar comes from a molecule containing two carbon atoms, four hydrogen atoms, and two oxygen atoms. And some molecules are made of thousands of atoms. Bread and potatoes contain giant molecules that look like chains – the chains have thousands of molecules.
Atoms and molecules follow the rules of chemistry and physics, even when they’re part of a complex, living, breathing being. If you learned in chemistry that some atoms tend to gain or lose electrons or form bonds with each other, those facts remain true even when the atoms or molecules are part of a living thing. In fact, simple interactions between atoms—played out many times and in many different combinations, in a single cell or a larger organism—are what make life possible. One could argue that everything you are, including your consciousness, is the byproduct of chemical and electrical interactions between a very, very large numbers of nonliving atoms!
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