Atomic Structure Timeline

Timeline created by opaz in Science and Technology

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Event Date:	Event Title:	Event Description:
09/02/500	400 B.C. Democritus	The Greek mathematician suggested that all matter was constructed of invisible indestructible particles called atoms that were not all identical and moves randomly about in a void.
09/02/1704	Isaac Newton	He theorised a mechanical universe with small, solid masses in motion
09/02/1803	John Dalton	He proposed that all matter consists of tiny particles called atoms that cannot be divided into smaller particles. The atoms of each element were different to one another because they had the different mass and atoms combined in simple whole number ratios.
09/02/1894	George Johnstone Stoney	Stoney theorised that electricity was comprised of negatively charged particles he called electrons.
09/02/1897	Joseph John Thomson	He proposed a model where atoms were positively charged spheres with negatively charged electrons embedded within. He discovered electrons in his experiments of electric discharge in a high-vacuum cathode-ray tube.
09/02/1900	Max Planck	Suggested the theory of quanta. He observed light emitted from hot, glowing objects.
09/02/1903	Hantaro Nagaoka	Proposed a ‘Saturnian model’ of the atom where negative electrons orbit the positive nucleus in flat rings.
09/02/1909	Robert Andrews Millikan	His ‘oil drop experiment’ determined the mass and the charge of electrons.
09/02/1911	Ernest Rutherford	His famous experiment where most radioactive alpha particles that were fired at a thin sheet of gold passed straight through proved that atoms were mostly empty space with a small, dense nucleus containing positive protons and negatively charged electrons orbited the nucleus.
09/02/1914	Henry Gwyn-Jefferys Moseley	He studied X-rays given off by various elements that gave off their own distinct wavelengths which could determined that the atomic number is equal to the number of protons in an atom.
09/02/1922	Niels Bohr	He suggested that electrons orbited the nucleus at different energy levels (shells). Only electrons with a specific amount of energy could be found in each shell.
09/02/1932	James Chadwick	Chadwick found neutral atomic particles similar in mass to protons using alpha particles. These were found in the nucleus and were named neutrons.
Timespan Dates:	Timespan Title:	Timespan Description:
09/02/1901 to 09/02/1932	Year