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Robert Boyle publishes The Skeptical Chemist and Aristotle's four-elements theory is disproved, leading to the "Death of Alchemy".
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John Dalton publishes his Atomic Theory stating that all matter is composed of small, indivisible atoms.
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Heinrich Geissler invents the first vacuum tube. It is used in chemistry to demonstrate the movement of electrons.
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Eugene Goldstein discovers positive particles, or protons, by using a tube filled with hydrogen gas.
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J.J. Thomson concludes that all atoms have negative charge and renames cathode rays electrons. He creates a model in which the atom shows a positively charged sphere with negatively charged electrons sticking to it.
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Robert Millikan discovered the mass of an electron by introducing charged oil droplets into an electrically charged field.
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Rutherford's model shows an atom containing a large amount of empty space, with a tiny dense positively charged nucleus surrounded by electrons traveling at extremely high speeds.
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Niels Bohr publishes what becomes known as the Bohr model, the theory that electrons travel in discrete orbits around the atom's nucleus.
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At Cambridge University, James Chadwick discovers the neutron, which will become crucial to the fission of uranium-235.
