When atoms join together by covalent bonding, they form particles called molecules. A molecule is a particle made up of two or more atoms joined together by covalent bonds.

The diagram below shows a molecule called ethanol. It is made up of two carbon atoms, six hydrogen atoms and one oxygen atom.

Diagram of an ethanol molecule. Atoms are represented by chemical symbols (C, O and H) and covalent bonds are represented by lines between atoms. There are two carbon atoms bonded to each other. The one on the left is bonded to three hydrogen atoms. The one on the right is bonded to two hydrogen atoms and one oxygen atom. The oxygen atom is also bonded to a hydrogen atom.

An ethanol molecule. It is made up of two carbon atoms, one oxygen atom and six hydrogen atoms joined by covalent bonds.

Molecules vary greatly in size. The smallest ones are made up of just two atoms. Ethanol is a fairly small molecule, consisting of nine atoms. There are some very large molecules which are made up of hundreds or even thousands of atoms.


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What is a molecule?


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