History of the Atom

Timeline created by TaylorBagley
  • 200

    Democritus

    Democritus
    Developed the first known idea of the atom around 460 B.C. He wondered how many times you could divide a piece of matter in half before you could not split it anymore. Thus, the idea of the atom was born.
  • 200

    Aristotle

    Aristotle
    In the 4th century B.C., Aristotle denounced the early theory of the atom, and because of his power and influence, the atom was not a consideration for the next 2000 years.
  • Antoine Lavoisier

    Antoine Lavoisier
    Known as the Father of Modern Chemistry- he discovered that water is derived from hydrogen and oxygen bondings together. In 1777, Laoisier presented the law of conservation of mass. Began discovering and naming elements, and explaining reactions between elements. John Dalton's atomic theory of 1803 is based upon Lavoisier's work.
  • John Dalton

    John Dalton
    Dalton's atomic model was simply a sphere.Proposed the atomic theory based on Lavoisier's earlier work. This theory stated five main things: elements are made of atoms, atoms can neither be created nor destroyed, atoms of the same element have the same mass, atoms of different elements have different masses, and atoms can only combine in whole number, small ratios. Unlike earlier suggestions of atoms, Dalton gave specific chemical measurements of each element.
  • Henri Becquerel

    Henri Becquerel
    Bequerel's model was known as the "plum pudding"Best known for his discovery of radioactive atoms at the turn of the 19th century. When he began work as a scientist in 1896, the X-ray had just been invented. Becquerel wanted to see if there were any connections between X-rays and the elements. He was awarded a Nobel Peace prize 1903 for discovering naturally occuring radiation in uranium.
  • J.J. Thomson

    J.J. Thomson
    In 1897, Thomson was in a laboratory experimenting with cathode rays, and deducted that atoms are made up of even a smaller matter, which he called "cospucles". After further experiments, he was proven correct, and the idea of the electron was confirmed.
  • Marie & Pierre Curie

    Marie & Pierre Curie
    This couples' work in radioactivity led them to the discoveries of the elements radium and polonium in 1898. They shared the Nobel Peace prize with Becquerel in 1903 for the discovery of radioactivity.
  • Max Planck

    Max Planck
    Created the quantum theory in 1900. This revolutionary theory explains the behavior and nature of energy down to a sub-atomic level. His works earned him a Nobel Pece prize in physics in 1918. His quantum theory was later used by Niels Bohr to present the model of an atom with quantized electronic states. The theory eventually developed into quantuum mechanics.
  • Ernest Rutherford

    Ernest Rutherford
    The atomic model got more and more developed through each passing scientist. This is an image of Rutherford's gold foil experiment.Rutherford studied under J.J. Thomson and developed Becquerel's idea of radioactivity into an exact proof that heavier atoms actually decay into radiation. In 1919 Rutherford discovered the proton. Finally, Rutherford discovered the half-life of radioactive elements.
  • Niels Bohr

    Niels Bohr
    Bohr's atomic model included electrons and their shells.Bohr adapted Rutherford's model of the atomic structure and tweaked it slightly. Bohr created the idea of electronic levels. Borh discovered that surronding the nucleus of an atom, containing both the protons and neutrons, were electron "shells".
  • Henry Moseley

    Henry Moseley
    Moseley studied under Ernest Rutherford. His main discvoeries led to a more accurate periodic table, due to more accurate measurements of atomic numbers. Moseley died in a car crash in 1915, when he was hardly in his 30's.
  • Robert Millikan

    Robert Millikan
    Millikan's oil drop experiment led heim to be able to determine the mass of an electron as being 1000 times smaller than the most basic atom.Experimentation led Millikan to find the elemtary charge of electricity. He also was able to confirm the atomic theory of matter. He proved J.J. Thomson's hypothesis that the mass of an electron is at least 1000 times smaller than the most basic atom.
  • Erwin Schrodinger

    Erwin Schrodinger
    Combined the equation for the behavior of waves with the de Brogile equation to make a mathematical model for the distribution of electrons in an atom. This model tells us where the elctron is most likely to be found in a certain region of the the atom at a certain time.
  • Werner Heisenberg

    Werner Heisenberg
    Stated the uncertainty principle, also known as "principle of indeterminancy". This principle states, "The more precisely the position is determined, the less precisely the momentum is known" when referring to any sub-atomic particle, such as an electron.
  • James Chadwick

    James Chadwick
    Chadwick, who was once a student under Rutherford, spent a lot of time trying to find a neutrral particle with enough mass to balance out a proton. Finally, after viewing experiments in Europe, he was able to gather sufficint evidence that the neutron did in fact exist. He recieved a Nobel Peace prize in 1935 for this magnificient discovery.