Basic Structure of Matter

After reading this section you will be able todo the following:

  • Give a basic definition of matter.
  • Describe a molecule.

The Atom

All matter such as solids, liquids, and gases, is composed of atoms. Therefore, the atom is considered to be the basic building block of matter. However, atoms are almost always grouped together with other atoms to form what is called a molecule. Only a few gases such as helium are composed of individual atoms as the structural unit. Click through the applet below to see the relationship between atoms, molecules, and compounds.

Atoms are extremely small. The radius of a typical atom is on the order of 0.00000000001 meters and cannot be studied without very powerful microscopes. Click through the applet below to see how a scanning electron microscope can be used to magnify things until very small details appear relatively big.

Throughout this module you will learn more about atoms and elements. 


  1. All matter is composed of atoms.
  2. A molecule is a group of atoms bunched together.