Concept preview

What you will be able to do

1. 01Outline how atomic models developed from Dalton to Bohr
2. 02Explain what the gold-foil experiment revealed
3. 03State the charge, mass and location of the three atomic particles

The idea of atoms is ancient — Democritus suggested uncuttable particles in the 5th century BC — but for two thousand years it remained philosophy. As late as 1900 some leading chemists doubted atoms existed, and the neutron was not found until 1932. The modern atom was pieced together over just a century of experiments, each model correcting the one before.