The History of the Atomic Theory- Catherine Schilling & Leandra Nikont P.7

  • Oct 3, 1450

    Printing Press Invented

    Printing Press Invented
  • Oct 23, 1492

    Christopher Columbus discovered America

    Christopher Columbus discovered America
  • Oct 3, 1543

    Copernicus Claims the Earth Circles the Sun

    Copernicus Claims the Earth Circles the Sun
  • America gained Independence from Britain

    America gained Independence from Britain
  • Cotton Gin Invented

    Cotton Gin Invented
  • Joseph Louis Proust

    Joseph Louis Proust
    In 1799, Proust published his findings and law of definite proportions which explained that if compounds are examined in their individual parts, they will continuously have the same proportions of their individual elements by weight. He also proposed the Law of Constant Composition which stated that the composition of a substance will always be the same, based on his previous findings.
  • John Dalton

    John Dalton
    Dalton had his own ideas about atomic theory. 1) Substances are made of atoms which cannot be created, divided, or destroyed. 2) Atoms of the same element are exactly alike. 3) Atoms combine with other atoms to create new substances.
  • First Photograph

    First Photograph
  • Eifel Tower built

    Eifel Tower built
  • J.J. Thomson

    J.J. Thomson
    Discovered negatively charged electrons which he called corpuscles. He disproved the part of Dalton's theory saying that atoms cannot be divided. He also recognized that there needed to be a positively charged part to balance the negative. Formed the Plum pudding model.
  • Ernest Rutherford

    Ernest Rutherford
    Rutherford introduced the existence of alpha and beta rays in uranium radiation. He also analyzed some of their properties. He and H. Geiger produced a method to detect an alpha particle and counting the number emitted from radium. Also, he and R.B. Owens discovered the isotope of radon, which is now known as thoron (a noble gas).
  • Henri Becquerel (1899-1900)

    Henri Becquerel (1899-1900)
    Becquerel, overall, made three contributions to the atomic theory. The first was that he measured the deflection of beta particles (a component of the radiation in magnetic/electric fields). He showed that the beta particle was also the same as Thomson’s, recently, discovered and not yet identified electron. Lastly he noticed that active substances in uranium would lose its radiation throughout time, but would regain its radioactivity over time again.
  • Max Planck

    Max Planck
    Planck discovered what he called quanta, non-continuous energy delivered in small pieces.
  • Robert Millikan

    Robert Millikan
    Millikan realized the single unit charge of any electron from an oil drop experiment at the University of Chicago, this allowed for calculation of mass of an electron and positively charged atoms. His equation was:
    e = 1.60 x 10-19 coulombs
  • Niels Bohr

    Niels Bohr
    Bohrs suggested that electrons move in definite paths in energy levels. The also suggested that they could switch paths.
  • World War I Began

    World War I Began
  • Louis de Brogllie

    Louis de Brogllie
    Brogllie introduced the idea that particles could sometimes behave as waves. With this is mind, waves could also behave as particles. He also introduced an equation to represent his findings:
    h=Planck's constant = 6.634x10-34 Js
  • Erwin Schrödinger

    Erwin Schrödinger
    Schrodinger created the basis for Bohr's model. It was called Schrodinger's wave equation used to find the probable location of an electron.
  • Werner Heisenberg

    Werner Heisenberg
    Although many rejected his ideas, Heisenberg ealized that if an electron was hit by gamma rays, to measure its properties, it would ultimately change the electron’s behavior. This idea became a fundamental law of nature.
  • James Chadwick

    James Chadwick
    Chadwick, with the help of Ernest Rutherford, discovered that there are neutraly charged particles in the neutron. He determined that neutrons, as he called them, had .1% more mass than the proton and that this accounted for the atomic mass being so large. However, he believed that the neutron was an electron and a proton paired together. None the less he won a noble prize for his discovery 1935.
  • World War II Began

    World War II Began
  • First use of Paper

    First use of Paper
    Paper replaced stone, slate, papyrus and vellum.