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More About Democritus VideoThis event occurred in 400 BC
Democritus's atomic theory revolves around the fact that atoms are present in the atmosphere. All atoms are present in solids and liquids and cannot be separated. Also, atoms do not have a specific size and can differ baesd on influences. -
More About the Law of Conservation of MassLavosier came up with and created the Law of Conservation of Mass. This law explains that during a chemical reaction, mass or matter is neither created or destroyed, only changed.
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Defined Law of Definite Proportion VideoProust observed a law of definite proportion. It states that when different elements combine to form a pure compound, the ratio stays the same.
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Dalton Video His TheoryDalton came up with a four part atomic theory, some of which holds true today and some that does not. Regardless, he actually just combined other scientists' work into his idea.
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More ReadingThe Plum Pudding Model VideoIn 1897, J.J. Thomson discovered the electron by using the cathode ray tube, and by 1904, he came up with a theory as to the structure of the atom. He proposed that the structure consisted of negatively charged electrons "floating" in a positively charged cloud. It got the name plum pudding model because it looked like plums in pudding.
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Gold Foil Experiment ExplainedRutherford used a gold foil experiment to study the atom. He hypothesized that the alpha (+) particles that he shot would all pass straight through the gold foil, however some deflected, with a few coming straight back. The experiment proved that the nucleus was small and positively charged, and that the atom was mostly empty space.
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More About His ExperimentMilikan used oil drops to determine the charge of an electron. He used x-rays to help him with noticing a charge. He successfully calculated the charge of an electron, and he also determined that the mass of an electron is 1/1840 the mass of a proton - electrons have virtually no mass!
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James Chadwick explaining His Finds More About the FindingIn 1932, James Chadwick discovered the nucleus after doing some experiments. When atoms of neon were found that had different masses, a third particle must be present, he said. It must have mass, but no charge. It was called the neutron.
