Atomic Theory Timeline

Timeline created by svraiders
  • 400

    Democritus - The Atom

    Democritus - The Atom
    More About Democritus Video*This event occurred in 400 BC*
    Democritus's atomic theory revolves around the fact that atoms are present in the atmosphere. All atoms are present in solids and liquids and cannot be separated. Also, atoms do not have a specific size and can differ baesd on influences.
  • Antoine Lavoisier - Law of Conservation of Mass

    Antoine Lavoisier - Law of Conservation of Mass
    More About the Law of Conservation of MassLavosier came up with and created the Law of Conservation of Mass. This law explains that during a chemical reaction, mass or matter is neither created or destroyed, only changed.
  • Joseph Proust - Law of Definite Proportion

    Joseph Proust - Law of Definite Proportion
    Defined Law of Definite Proportion VideoProust observed a law of definite proportion. It states that when different elements combine to form a pure compound, the ratio stays the same.
  • John Dalton - Atomic Theory

    John Dalton - Atomic Theory
    Dalton Video His TheoryDalton came up with a four part atomic theory, some of which holds true today and some that does not. Regardless, he actually just combined other scientists' work into his idea.
  • J.J. Thomson - Plum Pudding Model

    J.J. Thomson - Plum Pudding Model
    More ReadingThe Plum Pudding Model VideoIn 1897, J.J. Thomson discovered the electron by using the cathode ray tube, and by 1904, he came up with a theory as to the structure of the atom. He proposed that the structure consisted of negatively charged electrons "floating" in a positively charged cloud. It got the name plum pudding model because it looked like plums in pudding.
  • Ernest Rutherford - Gold Foil

    Ernest Rutherford - Gold Foil
    Gold Foil Experiment ExplainedRutherford used a gold foil experiment to study the atom. He hypothesized that the alpha (+) particles that he shot would all pass straight through the gold foil, however some deflected, with a few coming straight back. The experiment proved that the nucleus was small and positively charged, and that the atom was mostly empty space.
  • Robert Millikan - Oil Drop Experiment

    Robert Millikan - Oil Drop Experiment
    More About His ExperimentMilikan used oil drops to determine the charge of an electron. He used x-rays to help him with noticing a charge. He successfully calculated the charge of an electron, and he also determined that the mass of an electron is 1/1840 the mass of a proton - electrons have virtually no mass!
  • James Chadwick - Neutron

    James Chadwick - Neutron
    James Chadwick explaining His Finds More About the FindingIn 1932, James Chadwick discovered the nucleus after doing some experiments. When atoms of neon were found that had different masses, a third particle must be present, he said. It must have mass, but no charge. It was called the neutron.