Atom 3

Atomic Theory Timeline

By bshannon

  • John Dalton

    John Dalton
    Dalton's atomic theory proposed that all matter was composed of atoms, indivisible and indestructible building blocks. While all atoms of an element were identical, different elements had atoms of differing size and mass. Dalton also stated that all compounds were composed of combinations of these atoms in defined ratios. He postulated that chemical reactions resulted in the rearrangement of the reacting atoms.

  • JJ Thomson

    JJ Thomson
    JJ Thomson-JJ discovered the electron within the atom. He discovered them using the “cathode ray tube” in which they passed an electric current through a vacuum tube and observed light in the tube traveling in a straight line. This led to the discovery of the electron.

  • Ernest Rutherford

    Ernest Rutherford
    While doing his “gold foil” experiment, Rutherford discovered that atoms contained a nucleus. He also discovered that there must be a positively charged particle, the proton. Thus the Rutherford atomic model was made a year later in 1911

  • Neils Bohr

    Neils Bohr
    Discovered that atoms have a heavily charged nucleus with the electrons at a distance circling around it. This would later be recognized as the first accurate model of the atom. He discovered this through intuition.

  • Irwin Schrodinger

    Irwin Schrodinger
    He came up with the quantum mechanical atomic model which shows the orbitals around the nucleus in constant motion. This was made to describe the function of waves. (“Electron cloud”)

  • James Chadwick

    James Chadwick
    Discovered the presence of the neutron and that it had no charge. It changed the model of the atom and allowed for the creation of atomic bombs. He discovered this through atomic disintegration.

  • Democritus

    Democritus
    One of the creators of the first basis for the Atomic Theory which stated that all objects are made up of little indestructible and indivisible things called atoms. However, his discovery was often questioned because he could not explain the chemical side of his 'atom' idea. Stated that the solidness of a material corresponded with the shape of the atoms involved. He came up with the theory purely by philosophical means.