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Hypothesised that everything is composed of atoms.
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Proposed a mechanical universe made of small solid masses in motion.
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Dalton proposes an ‘atomic theory’ with atoms that are spherical and solid with masses based on measurable properties of mass.
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Stoney proposes that discrete negative particles he called electrons made up electricity.
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J.J. Thomson determines the charge to mass ration of an electron =1.759x108 coulombs/gram by using a CRT. He also discovered that canal rays were associated with the proton H +.
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Planck explains hot glowing matter with the idea of quanta(discrete units of energy).
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Nagaoka hypothesises that a model of the atom would look similar to the planet Saturn with flat rings of electrons circling around a positively charged particle.
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Oil drop experiment determined the charge (e=1.602 x 10 -19 coulomb) and the mass (m = 9.11 x 10 -28 gram) of an electron.
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Rutherford establishes that the nucleus of an atom is very dense and small and positively charged by using alpha particles as atomic bullets and probing the atoms in a piece of thin gold foil.
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Moseley writes"The atomic number of an element is equal to the number of protons in the nucleus" statement. Used x-ray tubes and determined the charges on the nuclei of most atoms.
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Developes an explanation of atomic structure that motivates regularities of the periodic table of elements. His atomic model had atoms built up of consecutive orbital shells of electrons.
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Discoveres a neutral atomic particle with a mass close to a proton using alpha particles.
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Conducts experiments to prove that heavy elements capture neutrons and form unstable products which undergo fission. This process ejects more neutrons continuing the fission chain reaction.
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Enrico Fermi conducts the first controlled chain reaction releasing energy from the atoms nucleus.