Atom

Atomic Theory Timeline

By Moretans
  • 460 BCE

    Democritus 460 BC - 370 BC

    Democritus 460 BC - 370 BC
    Atoms constantly move.
    Atoms are “uncuttable.”

  • John Dalton

    All substances are made of atoms.
    Atoms of the same element are exactly alike.
    Atoms of different elements are different.
    Atoms of the same element are exactly alike.
    He conducted experiments in combining elements.
    Atoms are small, hard particles.

  • Ernest Rutherford(August 30, 1871- October 19, 1937)

    Ernest Rutherford(August 30, 1871- October 19, 1937)
    He conducted the gold foil experiment.
    He conducted experiments in combining elements.
    Most of an atom’s mass is in the nucleus.
    There is a small, dense, positively charged nucleus.
    Atoms contain mostly empty space.

  • J.J. Thomson

    There are small, negatively charged particles inside an atom.
    He conducted the cathode-ray tube experiment.
    His theory of the atomic structure led to the “plum-pudding” model.

  • Niels Bohr

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

  • Erwin Schrӧdinger and Werner Heisenberg

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