All matter is made up of atoms, the basic unit of a chemical element. This is something we now take as a given, and one of the things you learn at the beginning of high school or secondary school chemistry classes.

Despite this, our ideas about what an atom is are surprisingly recent: as little as one hundred years ago, scientists were still debating what exactly an atom looked like.

This infographic takes a look at the key models proposed for the atom and how they changed over time:  from Democritus, to Bohr, and through till the quantum mechanical models.


History of Atomic Theory