Atomic theory

Atomic Theory Timeline

By gruichdl2020
  • 460 BCE

    Democritus

    Democritus
    Atoms are "uncuttable".
    Atoms are small, hard particles.
    Atoms constantly move.
  • 460 BCE

    Democritus's Atom

    Democritus's Atom
    Democritus' atom model was just a sphere, so he could further theorize.

  • John Dalton

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

  • Dalton's Atom

    Dalton's Atom
    Dalton thought since atoms were the smallest particle in the world, they were small hard spheres, such as billiard balls. This is where he came up with his model the "Billiard Ball" model.

  • J.J. Thomson

    J.J. Thomson
    Conducted the cathode-ray tube experiment.
    His theory of the atomic structure led to the "plum-pudding" model.
    There are small , negatively charged particles inside an atom.

  • Thomson's Atom

    Thomson's Atom
    Thomson proposed this model in 1898, he thought of the "Plum Pudding" model after he discovered the electron.

  • Ernest Rutherford

    Ernest Rutherford
    Atoms contain mostly empty space.
    Electrons move in empty space in the atom.
    Conducted the gold-foil experiment.
    Most of an atom's mass is in the nucleus.

  • Rutherford's Atom

    Rutherford's Atom
    Rutherford discarded the "Plum Pudding" model, and said that alpha particles could only be deflected backwards if the most of the mass of the atom was in the nuclues.

  • Niels Bohr

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

  • Bohr's Atom

    Bohr's Atom
    This model shows a nucleus surround by electrons on different paths. This is sometimes called the "Planetary" model since it looks like the sun with the electrons being the planets orbiting.

  • Erwin Schrödinger & Werner Heisenberg

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

  • Schrödinger's Atom

    Schrödinger's Atom
    Schrödinger took Bohr's model to the next level. He used mathematical equations to describe the likelihood of finding an atom in a certain position.