Later This site tells the story of the history of the universe. Click Earlier and Later to follow the story. An oxygen atom can bond with two hydrogen atoms to make a molecule we call water.
Water is an example of a compound, because it contains more than one kind of atom.
The formula for water is H 2 O, meaning there are two hydrogen atoms for each oxygen atom. This joining up of atoms is very lucky. Without it there would be no planets , no life , no people . They can do things which separate atoms never could. They will play a special part in our story.