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Democritus hypothesises everything is made of atoms
Hypothesised that everything is composed of atoms. -
Newton proposes a mechanical universe
Proposed a mechanical universe made of small solid masses in motion. -
Dalton proposes an 'atomic theory'
Dalton proposes an ‘atomic theory’ with atoms that are spherical and solid with masses based on measurable properties of mass. -
GJ Stoney names electrons
Stoney proposes that discrete negative particles he called electrons made up electricity. -
J.J. Thomson determines the charge ratio of an electron
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 +. -
Planck explains hot glowing matter
Planck explains hot glowing matter with the idea of quanta(discrete units of energy). -
Nagaoka hypothesises a model of the atom
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. -
Millikan determines the charge and mass of an electron
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. -
E. Rutherford established that the nucleus of an atom is very dense and small
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. -
H.G.J. Moseley discoveres that the atomic number is equal to the number of protons in the nucleus
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. -
Bohr develops and explanation of atomic structure
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. -
James Chadwick disvovers a neutral atomic particle
Discoveres a neutral atomic particle with a mass close to a proton using alpha particles. -
Lise Meitner proves that heavy elements capture neutrons
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. -
Enrico Fermi conducts first controlled chain reaction releasing energy from the nucleus
Enrico Fermi conducts the first controlled chain reaction releasing energy from the atoms nucleus.