Molecule vs Compound

So what is a molecule? In this chemistry tutorial, you will learn the difference between a molecule vs compound. They are very similar, but there are important differences! Every compound has molecules, but not every molecule is part of a compound.

The Role of Chemical Bonds 

Atoms chemically bond with other atoms in order to achieve “balance,” a term that denotes a decrease in reactivity. This stability is achieved via different electrostatic attractions that hold these bonds in place; the new grouping is more stable, and less reactive, than its original parts. 

In order to ensure stability during chemical bonding, atoms adhere to the “Octet Rule.” This guideline states that strong, steady bonds are generated when atoms achieve eight electrons in their outer (valence) shells. While some exceptions exist, the rule generally explains why atoms of certain elements tend to bond with each other. This joining of atoms is one of the fundamental concepts in chemistry, and it relates to our understanding of chemical reactions.

Within the realm of octet-seeking chemical bonding exist two distinct subdivisions: molecules and compounds. All compounds can be classified as molecules, but not all molecules can be called compounds. While this idea may appear confusing at first glance, the difference between the two categories is, in actuality, quite simple. 

Molecule vs compound tutorial example

Molecules vs Compounds: Which is Which? What is a molecule

Definition of a Molecule

A molecule forms when an atom bonds with other atoms; this may include atoms of the same element as this first atom, or those from different elements. Another definition of a molecule is an electrically neutral group of two or more atoms held together by chemical bonds. A molecule is the smallest particle into which an element or a compound can be divided without changing its chemical and physical properties. Learn what is an element in chemistry.

Definition of a Compound

A compound, on the other hand, must involve an atom bonding with atoms of two or more different elements. It thus always contains more than one type of element; its constituent parts combine in a fixed ratio. This information holds with the initial statement that all compounds are molecules, but not all molecules are compounds. As compounds contain atoms of different elements, they represent a subset of the molecule category. Molecules that include combinations of solely one type of atom, then, are not compounds, but elements. 

Examples of Molecules and Compounds 

What is a molecule? Example of the compound NaCl, otherwise known as table salt - which is composed of molecules

To help you practice discerning between molecules and compounds, here are some useful examples of both categories. Notice how all of the compounds hypothetically could be added into the molecule list, but that not every molecule could be moved to the compound list. We hope you now better understand molecule vs compound!

Examples of Molecules:

These are examples of molecules. Note that all of them consist of more than one atom, but not always more than one type of atom.

  • N2 (nitrogen)
  • I2 (iodine)
  • H2O (water)
  • O3 (ozone)
  • CaO (calcium oxide)
  • C6H12O6 (glucose)

 All compounds are molecules, but not all molecules are compounds

Examples of Compounds:

Here are examples of compounds. Notice that all of these compounds, contain more than one element.

  • NaCl (salt)
  • NaHCO3 (baking soda)
  • H2O2 (hydrogen peroxide)
  • C2H6O (alcohol)
  • CH4 (methane)
  • C55H72O5N4Mg ( chlorophyll)

Examples of Molecules that are not Compounds

These molecules are elements, not compounds. The first two examples are diatomic elements.

  • Cl2 (chlorine)
  • H2 (hydrogen)
  • O3 (ozone)