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Democritus theorized about matter being made of tiny particles
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Aristotle thought that all matter was made of 4 basic elements
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Alchemists theorized that all metals were made of sulfur and mercury
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Robert Boyle thought the elements could not be split into smaller forms
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John Dalton thought that atoms were indestructible building blocks of matter
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Dmitri Mendeleev made the first periodic table
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J. J. Thompson discovered the first electron
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Robert Millikan helped to quantify the charge of the electron
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Rutherford found that the atom is mostly empty space
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He invented the Geiger counter with measures radiation. He also helped with the gold foil experiment, which showed the atomic nucleus.
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He created the Bohr model, which showed that electrons could have stable orbits around their nucleus
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