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400
Democritus
In 400 B.C. he said that was composed of small particles called atoms. -
Lavoisier
Lavoisier VideoIn the 100's he made measurements of a chemicle in a sealed container. He came up with the Law of Conservation of Mass (Matter). This states that matter can't be created or destroyed. -
Proust
He came up with the Law of Definite Proportion, which said that a compound will always have the same composition regardless of their source. -
Dalton
He is considered to the father of atomic theory. He came up with the Law of Multiple Proportion. It states that combinations of the same elements can have different compunds. -
Thomson
Cathode rayHe did an experiment with a cathode ray and he developed the "Plum pudding" model of the atom. -
Millikan
Oil Drop experimentHe performed the Oil Drop experiment, and found that the mass of an electron was equal to 0. -
Rutherford
Gold foil ExperimentHe came up with the Gold Foild Experiment and concluded that atoms must be mostly empty space and the have to have a small, dense center called the nucleus. -
Chadwick
He discovered the neutron, and he said that it had a mass of 0.