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Belived in 4 elements, fire, water, earth, air. Refuted Democritus
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Found atoms were simplist unit of measure
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Thought if the four elements that made up everything:earth, air, fire, and water
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It is what makes thing burn
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Matter can omly change form not be destroyed
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Law of Definite Proportions
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Made atomic theory
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The proton was found
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Dimitri Mendeleev crested the first periodic table organized in 7 groups
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Proton was first found
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Found that uranium ore is radioactive
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The mass and charge of the electron was first found by Robert Millikan.
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Niels Bohr crested the atomic model
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Neutrons were discovered by James Chadwick
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Glenn Seaborg