Remember we learned that ions are atoms with a mismatched number of protons and electrons.
When these mismatched atoms meet up with other mismatched atoms,
they can stick together to become a bunch of atoms, called a molecule.
![](https://upload.wikimedia.org/wikipedia/commons/thumb/b/b4/Water-3D-balls.png/320px-Water-3D-balls.png)
(from: wikipedia - properties of water)