May 31, 2020
For educational institutions
Physics Atom Timeline
⟶ Updated 1 Nov 2017 ⟶
List of edits
350 BC Aristotle felt that there was no smallest part of matter and that different substances were made of earth, fire, air, and water.
442 BC Democritus discovered that all matter is made up of invisible particles called atoms.
1803 John Dalton created the Atomic Theory of Matter, in which all matter is made of atoms and that atoms cannot be created nor destroyed.
1897 J.J. Thomson discovered the electron, which led him to create the "plum pudding" atomic model.
1909 Ernest Rutherford believed that all the positive matter was in the center of the atom (nucleus) , surrounded by electrons.
1913 Neils Bohr improved Rutherford's atomic model, with electrons orbiting the nucleus
1926 Erwin Shrodinger's new model described how electrons move in wave form
1932 James Chadwick discovers the neutron which helps balance out the protons in the nucleus
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