Water's Compositions

A graphic showing how 2 hydrogen atoms and 1 oxygen atom make up H20.

What is Water Made of?

Everything is made of atoms. An atom is the smallest particle of an element, like oxygen or hydrogen. Atoms join together to form molecules. A water molecule has three atoms: 2 hydrogen (H) atoms and 1 oxygen (O) atom. That's why water is sometimes referred to as H2O. A single drop of water contains billions of water molecules.
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