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In 440 BCE, Democritus belived that all atoms were the smallest thing, and that they were made up of the same substance.
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He belived that all mater was made of atoms and that atoms were indestructable, all the atoms in an element are the same, coumpoundes were formed by mixing two different atoms, and a chemical reaction is the rearrangement of atoms. His model was billiard balls
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He discovered that atoms could be broken down and the existance of the electron. His model was the cathode ray tube expirement.
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Rutherford discovered that the center of an atom was posotive, and it was surrounded by negative electrons. Rutherford thought that the atom was mostly empty space. His most famous expiriment was the gold foil expiriment.
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In 1932, Chadwick discovered the existance of the nuetron. Chadwicks model was similar to Bohr's but with the existance of nuetrons.
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Bohr thought that electrons travel in stationary orbits around the atom using angular momentum. He used the Bohr model also known as the Planetary model.
