Atomic Theory

By JoshYn
  • 430 BCE

    Democritus

    Democritus
    Atoms are "uncuttable."
    Atoms are small hard particles.
    Atoms are made of a single material formed into different shapes and sizes.

  • John Dalton

    John Dalton
    All substances are made from atoms.
    Atoms of different elements are different.
    Atoms of the same element are exactly alike.
    He conducted experiments in combining elements.
    He wanted to know why elements combine in specific proportions.

  • J. J. Thomson

    J. J. Thomson
    There are small negatively charged particles inside the atom.
    His theory of atomic structure led to the plum pudding model.
    He did the cathode ray tube experiment.

  • Rutherford

    Most of an atom's mass is in the nucleus.
    Gold foil experiment.
    There is a small dense positively charged nucleus.
    Atoms contain mostly empty space.
    His model had electrons surrounding the nucleus at a distance.

  • Bohr

    Electrons travel in certain paths, or energy levels.
    Electrons can jump from a path in one level to a path in another level.

  • Schrodinger and Heisenberg

    Electron paths can't be predicted.
    Electrons are found in clouds and not paths.

  • Chadwick

    Discovered the neutral Nuetron