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  He was the first person to identify the possibility of an atom. He described an indivisible, sphere, solid model.
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  Aristotle dismissed Democritus’ atom as “worthless.” Said that the four elements were earth, fire, air and water.
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  Father of modern atomic theory; five parts of his atomic theory including that elements are composed of atoms and that element’s atoms are identical in mass.
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  Discovered the electron. He also designed the Plum Pudding model.
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  Determined the charge and mass of an electron through the oil drop experiment.
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  Said that an atom has a small positive nucleus and the remainder is empty space through the gold foil experiment. He designed a model which is called the Nuclear model.
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  He stated that the atomic number of an element is equal to the number of protons in the nucleus. Designed the periodic table according to atomic mass.
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  Predicted that electrons travel in specified energy levels. He described a model which looks like the planets in the solar system called Planetary model.
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  Worked with Einstein to determine that electrons were similar to particles and waves.
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  Came up with the “uncertainty principle”: It is impossible to determine the position and momentum of a particle at the same time. Finalised the Quantum Mechanical Model.
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  Viewed electrons as a cloud and introduced wave mechanics as a model for the atom.
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  Discovered the neutron.
