Atomic Discoveries


Thinking about matter

442 BC

Democritus, a greek philosopher, along with his teacher, Leucippus, thought that all matter was made of invisible elements

Atoms and John Dalton


John Dalton, a British chemist and physicist, developed a theory that all matter is made of atoms that have different weights. He also proposed that these atoms are spherical and are in constant motion.

Cathode Ray Tube


A primitive cathode ray tube was invented by Sir William Crookes.

Radiation and atoms


The theory that radioactive particles cause atoms to break down then taking the form of energy and subatomic particles is theorised by Pierre and Marie Curie.

Electrons discovered


JJ Thomson discovers the electron, using cathode rays

Early Quantum Theory


Max Planck introduced the quantum theory - stating that electromagnetic energy could only be emitted in quantized form.

Einstein and light


Einstein creates special theories of relatively and hypotheses about the particle nature of light.

Charge of electron measured


Robert Millikan measures the charge of a single electron.

Structure of an atom developed


Ernest Rutherford developed the theory for the structure of an atom.

Bohr improves the atomic model


Neils Bohr developed the Bohr atomic model, with electrons travelling around the nucleus and the chemical properties being determined by the number of electrons.