Atomic Theory Timeline

  • Democritus
    440 BCE

    Democritus

    Atoms are "uncuttable."
    Atoms are small, hard particles
    Atoms constantly move
  • Demoritus
    440 BCE

    Demoritus

    Atomic Model
  • John Dalton

    John Dalton

    He conducted the cathode-ray tube experiment
    He conducted experiments in combing elements
    Elements combine in specific proportions
    Atoms of the same element are exactly alike
    Atoms of different elements are different
    All substances are made of atoms
  • John Dalton

    John Dalton

    Atomic Model
  • J.J Thomson

    J.J Thomson

    There are small, negatively charged particles inside an atom
    The atomic structure lead to the "plum pudding" model
  • J.J Thomson

    J.J Thomson

    Atomic Model
  • Ernest Rutherford

    Ernest Rutherford

    There is a small, dense, positively charged nucleus
    Most of an atom's mass is in the nucleus
    He conducted the gold foil experiment
    Electrons move in empty space in the atom
    Atoms contain mostly empty space
  • Ernest Rutherford

    Ernest Rutherford

    Atomic Model
  • Niels Bohr

    Niels Bohr

    Electrons travel in definite paths
    Electrons jump between levels from path to path
  • Niels Bohr

    Niels Bohr

    Atomic Model
  • Erwin Schrodinger and Werner Heisenberg

    Erwin Schrodinger and Werner Heisenberg

    Electrons are found in electron clouds, not paths
    Electron paths cannot be predicted
  • Erwin Schrodinger and Werner Heisenberg

    Erwin Schrodinger and Werner Heisenberg

    Atomic Model