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All matter is made up small indestructible units he called atoms.
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Theorized a mechanical universe with small, solid masses in motion.
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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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That electricity was comprised of negative particles he called electrons.
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Determined the charge to mass ratio of electrons.
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Proposed the idea quantization to explain how a hot, glowing object emitted light.
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Proposed an atomic model called the Saturnian Model to describe the structure of the atom. It was used for him to show that he predicted that an atom had a very massive nucleus and there are electrons revolving around the nucleus, bound by electrostatic forces.
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Accurate determination of the charge carried by an electron, using the elegant "falling-drop method." He also proved that this quantity was a constant for all electrons.
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Theorized that atoms are constructed much like the solar system. That is, a heavy part, called the nucleus, forms the centre of each atom. Particles with a negative charge, called electrons, form the outer part, most of which consists of an empty space. Discovered alpha, beta, and gamma rays in radiation.
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Discovered that the number of protons in an element determines its atomic number.
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Proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit.
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Discovered neutrons, particles whose mass was close to that of a proton.
