History of the atomic model

Democritus' concept of the atom

500

Democritus proposed the existence of atoms.
Limited technology at the time meant this was just an idea and could not be tested.

Dalton's atomic theory

1804

Dalton developed his theory of atoms and matter.
Experiments in chemistry and careful measurement of results allowed Dalton to support his hypothesis with evidence.

plum pudding

1897

JJ Thomson discovered the electron.
Experiment using electric charges in cathode ray tubes.

Rutherford's planetary model

1911

Rutherford developed the planetary model of the atom.
Experiment using alpha particles fired at thin gold foil and an early prototype Geiger counter to measure results.

Bohr's model

1913

Bohr developed a model of the atom.
Bohr used mathematical models and laws of quantum physics to propose his updated model.

Chadwick- bohr model

1932

The neutron was discovered by James Chadwick.
Experiments using kinematics and accurate measurements lead to proving the existence of a previously undetected subatomic particle, the neutron.