Atomic Theory Timeline

  • 460


    him and his teacher Leucippus theorized that the world consisted of two necessary principles, atoms and void. Atoms are indivisible and indestructable. There are a variety of shapes and sizes. They move through the void, bouncing off each other. Sometimes, they become hooked and form clusters which are different substances we know today.
  • Isaac Newton

    Isaac Newton
    This fellow introduced the laws of gravitation, atoms were held together by attractions called forces. He adapted atomism to fit the God's role in creation. Light was also of some kind of atoms and Solar rays were streams of particles.
  • John Dalton

    John Dalton
    Credited for the first modern atomic theory.
    - All matter consisted of tiny indivisible particles which he called Atoms
    - All atoms of a particular element are alike, but they different elements have different atoms.
    - Atoms are unchangeable
    - Atoms of elements combine to form compound atoms
    - In chemical reactions, atoms are neither created or destroyed, but rearranged.
  • George Johnstone stoney

    George Johnstone stoney
    Most famous for introducing the word electron as the "fundamental unit quantity of electricity". Developed the concept at around 1874 and the term was used in 1891. He published around 75 papers during his lifetime.
  • Joseph John Thomson

    Joseph John Thomson
    Credited for the discovery of the electron and of isotopes. He invented the mass spectromer and was awarded the 1906 Nobel Prize in Physics for the discovery on the electron and for his work on the conduction of electricity in gases.
  • Max Planck

    Max Planck
    Established the Quantum theory in which energy can only be absorbed or radiated in discrete volumes of Quanta. He was awarded the Noble Prize in Physics in 1918.
  • Hantaro Nagaoka

    Hantaro Nagaoka
    Proposed that the atom nucleus was large and positively charged and electrons that orbited the nucleus were bound by electrostatic forced. Developed an incorrect "Saturnian" model of the atom with flat rings of electrons revolving around a positively charged particle based on his fascination on the planet, Saturn. Proved that electrons moving around the nucleus were bound by electrostatic forces- like gravitational pull keeping the rings of Saturn revolving.
  • Robert Andrew Millikan

    Robert Andrew Millikan
    Found the charge of an electron through an oil-drop experiment and found the charge to be 1.592 x 10-9 coulomb which is lower than the now 1.602 176 53(14) x 10−19 coulomb due to use of inaccurate value for the vicosity of the air.
  • Ernest Rutherford

    Ernest Rutherford
    He devised the Rutherford model, which is a model of the atom with a positive charge concentrated in a very small nucleus. He also made the discovery of protons and suggested the idea of neutrons in the nucleus. He is credited with first splitting the atom in 1917.
  • Henry Gwyn-Jeffreys Moseley

    Henry Gwyn-Jeffreys Moseley
    Henry Gwyn-Jeffreys Moseley arranged the periodic table according to the atomic number of the elements. He introduced a law concerning the characteristic x-rays that are emitted by atoms.
  • Niels Bohr

    Niels Bohr
    Created the Bohr model of the atom which showed that electrons moved in specific orbits and the shell model of the atom in which an element’s chemical properties are determined by the number of electrons in the outermost orbit.This also showed why electrons are stable in an atom.
  • James Chadwick

    James Chadwick
    This man was an english nobel laureate in physics awarded for his discovery of the neutron. His discovery made it possible to create elements heavier than Uranium in the laboratory.