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Democritius discoadeverd matter is made of small indiviual paricles which have different forms postions and arrangements, which he named atoms.
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Dalton developed the atom theory, stating that spherial atom have measured propertied of mass. He also develped the concept of moles.
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Goldstein discoverd canal rays which are postively charged equal to an atom.
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Thompson discoverd the negatively charged electron in the cathode ray tube. He datermined that the electron was a component of all matter and calculated the charge to mass ratio for the electron. It is e/m= 1.76 x 10^8 coulombs/grams. He also discover protons are too associated with canal rays.
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Millikan determined the unit charge of an electron by performing an oil-drop experiment. The formula is e+ 1.60 x 10^-19 coulombs.
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Rutherford found that an atom has a small, dense, postively charged nucleus, and that the electrons move around the nucleus.
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Bohr discovered how electrons move in a circular orbit at a fixed distance from the nucleus.
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Schrodinger developed a mathematical equation to describe the motion of electrons in atoms. His work leads to the electron cloud model.
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Chadwick confirmed the extistance of neutrons which have no charge Atomic nucluei contain neutrons and postively chraged protons.
