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Aristotle proposes the four element theory: earth, air, fire & water
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Democritas and Leucippus proposed the idea of an atom
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Robert Boyle published "The Sceptical Chymist" which was a treatise on the distinction between chemistry and alchemy. It also contained some of the earliest ideas of atoms, molecules, and chemical reaction marking the beginning of the history of modern chemistry
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John Dalton proposed "dalton's Law" describing the relationship between the compnents in a mixture of gases.
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Jakob Berzelius developed a table of atomic weights & introduced letters to symbolize elements
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First Organized Periodic Table
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William Ramsay discovered the Noble Gases.
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J.J. Thomson discovered that the atom had Electrons
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Ernest Rutherford discovered the source of radioactivity as decaying atoms
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It was thought that Electrons orbited the Nucleus like planets orbited the sun.
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Rutherford discovered that an atom contained a proton
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James Chadwick discovered that an atom has Neutrons
