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350
Aristotle
Did not believe ancient Greek theory that atoms were different sizes. developed theory that matter consisted of different elements Fire, Water, Earth, and Air. Aristotle also believed that they had four qualities which were Coldness, Hotness, Dryness and Moistness. this theory was used for about 2,000 years -
Period: 350 to
Atomic development
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400
Democritus
Democritus wondered if atoms could be split into smaller pieces. He found out they they could not. And Democritus said that atoms were indivisible.He was the first to believe that the atom was the smallest piece of matter -
John Dalton
Dalton believed that all matter was made of atoms and that they were indivisible and indestructable. He also believed that all atoms of an emlemnt had the same mass and properties. He thought that compounds were a combination of two different types of atoms. Finally he believed that a chemical reaction was a rearrangement of atoms. -
Joseph John Thomson
Thomson discovered that the atom was made up of small particles. These particles are electrons. Thomson proved his theory using the cathode ray tube. this is known as the plum pudding model. -
Max Planck
Planck is considered the founder of the quantum theory. his theory revolutionized the way we look at atomic and subatomic processes. -
Ernest Rutherford
Rutherford overturned Thomson's model in 1911 with his well-known gold foil experiment in which he demonstrated that the atom has a tiny, heavy nucleus. Rutherford designed an experiment to use the alpha particles emitted by a radioactive element as probes to the unseen world of atomic structure. -
Niels Bohr
Bohr created the Bohr model. Also 1915 and 1918 Planetary model of Atom Electrons travel in specified energy levels Spectrum lines produced when electrons move. -
Robert Millikan
Millikan used the oil drop experiment to help his discoveries. he found that an electron is more than 1000 times smaller than an atom -
Erwin Schrodinger
the Schrodinger model assumes that the electron is a wave and tries to describe the regions in space, or orbitals, where electrons are most likely to be found. -
Werner Heinsberg
Werner is remembered for discovering the uncertainty principle. he said that this proves electrons do not travel in neat orbits and that all electrons that contain photons will then change momentum and physics. -
James Chadwick
James was most famous for his discovery of the neutron in an atom.
Which took place in 1932. -
Louis de Broglie
His ideas were a basis for developing the wave mechanics theory. This theory has greatly improved our knowledge of the physical nature on the atomic scale. He received the Nobel Prize for Physics on his wave nature of electrons discovery in 1929.