Atomic Discoveries

Events

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

1803

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

1870

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

Radiation and atoms

1898

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

1898

JJ Thomson discovers the electron, using cathode rays

Early Quantum Theory

1900

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

Einstein and light

1905

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

Charge of electron measured

1908

Robert Millikan measures the charge of a single electron.

Structure of an atom developed

1909

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

Bohr improves the atomic model

1913

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