What Is the Difference Between a Molecule and a Compound?

Every compound is a molecule, but not every molecule is a compound

This is the three-dimensional structure for ozone, which consists of three oxygen atoms bonded together. Ozone is a molecule, but not a compound.
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by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated December 11, 2019

A molecule is formed when two or more atoms of an element chemically join together. And a compound is a type of molecule, in which the types of atoms forming the molecule are different from each other.

Not all molecules are compounds, because some molecules, such as hydrogen gas or ozone, consist only of one element, of only one type of atom.

Molecule Examples

Some examples of molecules include:

Compound Examples

Some examples of compounds include:

  • Salt: NaCl
  • Water: H2O