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Aristotle describes his idea of five elements of Matter. Aristotle believed that all matter was made up either of one of the elements of water air earth and fire or combinations of these four elements, with the exception of stars and planets which were made of aether
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Democritus developed the idea of an atom.
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Lavoisier observes that heating mercuric oxide produces metallic mercury.
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He thus enunciated Gay-Lussac's law or J.A.C. Charles's law, published in 1802 came up with his own atomic theory.
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They established that the heavy element thorium was radioactive and discovered two new elements: polonium and radium.
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Henri Becquerel researched the newly discovered X-rays it led to studies of how uranium salts are influenced by light.
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He discovered the atom.
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He discovered alpha and beta rays
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Max Planck discovered the quantum physics/theory.
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Niels Bohr proposed a theory for the hydrogen atom based on quantumtheory that energy is transferred only in certain well defined quantities.
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Observed the properties of x-rays from about a dozen consecutive elements in the periodic table. In doing so, he discovered that the wavelength of the x-rays became shorter as the atomic weight increased.
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He discovered the charge and mass values or an electron.
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Discovered a way to formulate quantum mechanics in terms of matrices.
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A powerful model of the atom was developed by Erwin Schrödinger.
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James Chadwick used scattering data to calculate the mass of this neutral particle to discover the neutron.
