Atomic Theory Time Line

  • Antoine Lavoisier

    He discovered elements, formulated a basic law of chemistry and helped create the metric system.
  • Law of conservation of mass

    Antoine Lavoisier discovered that mass is neither created nor destroyed in chemical reactions.
  • John Dalton

    John Dalton
    Atomic Theory was a break through in our shelers traveling of matter.
  • Dalton's Atomic Theory

    -All matter is composed of atoms.
    -Atoms cannot be made or destroyed.
    -All atoms of the same element are identical.
    -Different elements have different types of atoms.
    -Chemical reactions occur when atoms are rearranged.
    -Compounds are formed from atoms of the constituent elements.
  • Cathode Ray Tube

    Physicist in the 19th century created a glass tube with wires inserted in both ends, and pumped out as much air as they could, an electric charge passed across the tube from the wires would create a flourescent glow.
  • Dmitri Mendeleev

    Dmitri created the first periodic table of the chemical elements.
  • Robert Millikan

    Discovered the charge of an electron with his oil drop experiment.
  • J.J. Thomson

    J.J. Thomson
    Earliest theoritical description of inner structure of atoms.
  • Gold Foil Experiment

    Gold Foil Experiment
    Ernest Rutherford studied the absorption of radioactivity by thin sheets of metal foil and found two components: alpha and beta.
  • Plum Pudding Atomic Model

    Each atom was a sphere filled with a positively charged fluid. The fluid was called the "pudding." Scattered in this fluid were electrons known as the "plums."
  • Democritus

    Believed that atoms are always moving and comes in different shapes and sizes.
  • Rutherford Model

    Ernest Rutherford conducted what is now a famous experiment where he bombarded gold foil with alpha particles. A source which undergoes alpha decay is placed in a lead box with a small hole in it. Any of the alpha particles which hit the inside of the box are simply stopped by the box. Only those which pass through the opening are allowed to escape, and they follow straight line to the gold foil.
  • Ernest Rutherford

    Rutherford proposed a new model for the atom. His experiments were the first to show that the atom must consist of a very tiny positively charged nucleus surrounded by negatively charged electrons. Rutherford also discovered and named alpha, beta, and gamma radiation.
  • Henry Moseley

    Henry Moseley showed that periodicity was a function of the atomic number rather than of atomic mass.
  • Niels Bohr

    Niels Bohr
    The atomic model in 1913. He described the nucleus as a compound structure in 1936.
  • Bohr Planetary Model

    Proposed that electrons travel only in certain successively larger orbits. he suggested that the outer orbits could hold more electrons than the inner ones, and that these outer orbits determined the atom´s chemical properties.
  • Electron Cloud Model

    Erwin Schrodinger created a new atomic model in the 1920´s. he described the atom with a positively charged nucleus, similar to Rutherford´s, and Bohr´s atomic models, with a cloud-like collction of electrons surrounding it. The cloud represents where the electrons could be, not where they are at a given moment. This model also insists that electrons travel randomly around the nucleus without any certain pattern.
  • Erwin Schrodinger

    Erwin Schrodinger
    He contributed papers of the scientific literature. He was also one of the most creative theoritical physcist. he discovered wave mechanics.
  • Quantum Mechanical Model

    Was constructed by Erwin Schrodinger. Electrons are defined as standing waves. The electron probability distribution gives the areas in which the probability of electron presence is high. The exact position of the electron is never known as stated by the Heisenberg.
  • James Chadwick

    Proved the exisence of neutrons, the elementary particle without any electrical charge and a fundamental building block of the atom´s nucleus.