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He formulated an atomic theory which stated that everything was composed of atoms. Democritus and his mentor, said that atoms can't be destroyed and are different in shape and size.
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He theorised a mechanical universe with small solid masses in motion and said that atoms in molecules are bind together by forces.
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Proposed an atomic theory which stated that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together.
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Introduced the "fundamental unit quantity of electricity" which was electrons. His contribution became part of the discovery of electrons.
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He discovered electrons and proposed the plum pudding model of the atom. When he discovered electrons, he knew that they had a negative charge and thought that matter must have a positive charge.
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He founded the quantum theory which showed that when atoms vibrate strong enough, it can cause objects to light up which would then measure the energy.
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Propsoed an atomic model, "Saturnian Model". The atom model, which made two predictions, was an analogy to the explanation of the stability of Saturn rings.
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Found the measurement of the charge and mass of a single electron while working on an oil drop experiment.
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With the results of an experiment, he suggested that electrons orbited around a positive centre.
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While studying the x-rays of various elements he saw that each element produced its own distinct set of wavelengths. He then showed that these x-ray wavelength could be better correlated with the atomic number which made him discover the number protons in an element determines its atomic number.
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In one of his experiment, he found that electrons can only orbit at a certain distance from the nucleus and an atom absorbs energy when an electron gets boosted from a low energy orbit to a high energy orbit.
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Discovered neutron which led onto the possibility to create elements heavier than Uranium.
