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Proposed his theory in 475 BC. He was the first greek to propose an atomic theory. He stated that everything is made of indivisible, imperishable elements called atoms. Democritus held this theory as well.
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Democritus states that everything is composed of atoms, they are physically, but not geometrically indivisible, and they are in constant movement. His mentor was Leucippus.
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He stated that an element is one of a kind (pure) because all atoms of an element are identical. All the atoms that make up the element have the same mass. All elements are different from each other due to differing masses.
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In the 1870s he deeply studied and discovered discovered the cathode rays. Goldstein deepest goal was the discovery of protons.
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JJ Thomson used Goldstein early research and it led to the discovery of electrons. He stated that the atom was a solid circle like element which had protons and electrons spread in itself.
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Ernest Rutherford was JJ Thomson's student, later on they worked together on the conductive effects of X-rays on gases, work which led to the discovery of the electrons, which Thomson presented to the world in 1987.
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Niels Bohr contributed to the understanding of atoms by designing his own model, and collaborating with other scientists like Rutherford. He developed the quantum theory.
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James Chadwick is mostly known for his discovery of the neutron, which alongside with the proton make up a atom's nucleus. He won 1935's physics Nobel prize.
