Development of the Atomic Model

By KHanusch
  • 400

    The Early Greeks

    The Early Greeks
    NOTE: The Date would be 400 BC More than 2000 years ago, the Greeks proposed that matter could only be made up of four elemental substances:
    Fire
    Earth
    Wind
    Water
  • 400

    Democritus

    Democritus
    In the 5th century B.C., Democritus proposed that all matter is made of individual, indestructible particles called atoms
    He had no scientific proof of this hypothesis

  • Robert Boyle

    1600’s – Identified gold and silver as being elemental
    His ideas were slowly accepted and additional elements were discovered
    The Greek concept of matter faded

  • John Dalton

    John Dalton
    Dalton's Atomic Theory
    - All elements are made of atoms and cannot be divided.
    - Only atoms of the same elements are identical.
    - Atoms can physically mix together or combine in whole number ratios
    - Atoms can never change their identity, only rearranged. (Like Legos)
    - Daltons model assumed atoms were like marbles or pool balls.

  • J.J. Thomson

    J.J. Thomson
    • Used cathode ray tube to discover the electron
    • Negative electrons were attracted to the positive side of the magnet.
    • Since all atoms are not magnetic, positive charges must be inside the atom to balance out the negative charges on the outside
    • New Model: (Plum Pudding)

  • Ernest Rutherford

    Ernest Rutherford
    The Rutherford model is a model of the atom devised by Ernest Rutherford. Rutherford directed the famous Geiger–Marsden experiment in 1909 which suggested, upon Rutherford's 1911 analysis, that the so-called "plum pudding model" of J. J. Thomson of the atom was incorrect.

  • Neils Bohr

    In atomic physics, the Rutherford–Bohr model or Bohr model, introduced by Niels Bohr in 1913, depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system, but with attraction provided by electrostatic forces rather than gravity.

  • Louis De Broglie

    Louis De Broglie
    Louis de Broglie, in full Louis-Victor-Pierre-Raymond, 7e duc de Broglie (born August 15, 1892, Dieppe, France—died March 19, 1987, Paris), French physicist best known for his research on quantum theory and for predicting the wave nature of electrons. He was awarded the 1929 Nobel Prize for Physics.

  • Erwin Schrodinger

    Erwin Schrodinger
    In 1926 Erwin Schrödinger, an Austrian physicist, took the Bohr atom model one step further. Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom.

  • Werner Heisenberg

    Werner Heisenberg
    Heisenberg developed his famous uncertainty principle, which he first described in a letter to Wolfgang Pauli, in 1927. The uncertainty principle states that the values of certain pairs of variables cannot both be known with complete precision, not so much due to the limitations of the researcher’s ability to measure them, but rather due to the very nature of the system itself.

  • James Chadwick

    James Chadwick
    In 1932, James Chadwick bombarded beryllium atoms with alpha particles. An unknown radiation was produced. Chadwick interpreted this radiation as being composed of particles with a neutral electrical charge and the approximate mass of a proton. This particle became known as the neutron.