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Developed the idea of an atom. Conceived the idea that matter was made up of minuscule, irreducible particles, which he called atoms, a name derived from the Greek word atomos, meaning indivisible. (460 B.C.)
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(322 B.C.) Claimed that there was no smallest part of matter (atoms) and that different substances were made up of proportions of fire, air, earth, and water.
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Came up with the Law of Conservation of Mass.
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Proposed the Law of Constant Composition.
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Stated that all matter is made of indivisible and indestructible atoms, which differ from element to element.The atom, it was assumed, was of uniform density and constitution. Discovered the Dalton theory. Law of Multiple Proportions.
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Avogadro's Hypothesis. The hypothesis states that at the same temperature and pressure, equal volumes of gases contain the same number of molecules or atoms
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Discovered cathode-ray tubes.
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Discovered the electron.
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Stated that radioactive materials cause atoms to break down spontaneously, releasing radiation in the form of energy and subatomic particles.
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Discovery radioactivity along with Madame Curie.
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Stated that energy is radiated in small, discrete units, which he called quanta.
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The existence of atoms of finite size
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Calculated mass of a single electron
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Found evidence that the atom really consisted of a highly dense nucleus and a vast empty space in which the electrons orbited.
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The atomic number was equal to the positive charge (charge on the nucleus) of an atom.
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Created Bohr Model.
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Suggested matter consists of waves.
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Schrödinger model. Explained movement of an electron in an atom as a wave.
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Uncertainty Principle, which says that the more precisely the position of a particle is determined, the less precisely the momentum is known in this instant, and vice versa.
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Proved that neutrons, neutral particles in the nucleus that made up approximately half the mass of an atom, did exist
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