Atomic Theory Timeline

By crooney
  • 364

    Aristotle

    Aristotle believed in the four elements of earth, wind, water, and fire. He also believed that a portion of matter could be cut in half infinitely many times. (364 B.C.)
  • 420

    Democritus

    Democritus was the first person to propose the existence of an ultimate particle. He described this particle using the word "atomos". He made this proposition in 420 B.C.
  • Oct 12, 1492

    Christopher Columbus discovers America

  • Galileo invents telescope

  • Shakespeare dies

  • U.S. gains independence

  • Joseph Proust

    Jospeph Proust proposed the law of Constant Composition which states that samples of a pure compond always contain the sam elements in the same mass proportion

  • John Dalton

    John Dalton proposed the Law of Multiple Proportions. This law led to the development of the atomic theory. He pictured the atom as a small indestuctible particle with no internal structure.
  • Period: to

    Mexican-American War

  • Period: to

    American Civil War

  • J.J. Thomson

    Thomson identified the negatively charged electron. He concluded that the electron was a component of all matter. He also proposed the "plum pudding" model of the atom.

  • Henri Becquerel

    Henri Bequerel discovererd natural radioactivity in elements.

  • Max Planck

    Max Planck developed the concept of quantum mechanics. His This concept served as the foundation for all modern physics and most atomic models.

  • Wright Brothers make first flight

  • Model T makes its debut

  • Robert Millikan

    Millikan dtermined the unit charge of the electron. His discovery allowed for the calculation of the electron and all positively charged atoms.

  • ernest rutherford

    Ernest Rutherford published an atomic theory in which the atom has a central positive nucleus surrounded by negative orbiting electrons.

  • Titantic sinks

  • Neils Bohr

    Bohr applied the quantum theroy to Rutherford's atomic structure and discovered a method of calculating the possible energy levels of stationary electrons. He also discovered that an emission of light occurs when an electron moves into a differnet energy level orbit.

  • Panama Canal opens

  • Louis De Broglie

    Broglie proposed that electrons could behave as waves under certain conditions.

  • Erwin Shrodinger

    Erwin Shrodinger developed the Shrodinger equation. This equation can be used to predict the properties reactivities of all atoms and molecules. His work led to the atomic cloud model.

  • Werner Heisenberg

    Werner Heisneberg discovered the Heisenberg Uncertainty Principle which states that the momentum and postion of a particle cannot be simultaneously measured with high precision.

  • James Chadwick

    James Chadwick confirmed the existence of the neutron.

  • D-Day

  • NASA lands on the moon