Atomic Theory Timeline

By neda919
  • 200

    Democritus (In between 460 and 370 BC)

    Democritus (In between 460 and 370 BC)
    Democritus came up with the idea that "nothing can change into something absolutely different." He named and discovered the atom, the “basic brick of matter” (thinkquest- Given Source). (Picture 6)
  • 304

    Aristotle (In between 384 and 322 B.C.)

    Aristotle (In between 384 and 322 B.C.)
    Aristotle challenged and disagreed with Democritus’ ideas about the atom by arguing that the world couldn't be made of small particles because if that was true, then the atoms should fall down like a rock does when it’s thrown in the air. Instead, Aristotle believed in four forces: dryness, wetness, heat and cold (thinkquest- Given Source). (Picture 11)
  • Jan 1, 1140

    The Abbey of Saint-Denis in Paris, a Gothic Styled Church, is Built

    (A History)
  • Jan 1, 1492

    Christopher Columbus discovers the “New World”

  • Jan 1, 1564

    Discovery of Graphite which led to the pencil

  • Ben Franklin's Kite is Struck by Lightning

    (Historical Events)
  • Congress adopted the Declaration of Independence

  • Joseph Proust

    Joseph Proust
    Proust created his law of definite proportions that said when compounds are broken down into their individual parts, they always have the same proportions of their elements by weight (Law of Definite Proportions). (Picture 13)
  • John Dalton

    John Dalton
    Dalton developed the idea that atoms are tiny, indestructible particles. He believes that these atoms have no internal structure (Book). (Picture 4)
  • Quantum Mechanics Created

    Quantum Mechanics Created
    (Picture 15 and Quantum Mechanics)
  • Lincoln Elected President

    (Abraham Lincoln)
  • Henri Becquerel

    Henri Becquerel
    During an experiment to fog up photographic film plates by exposing uranium salts to sunlight, Becquerel accidently discovered radiation (Book). (Picture 8)
  • J.J. Thomson

    J.J. Thomson
    Thomson determined the ratio of charge, to a molecule’s mass; cathode radiation. He discovered the electron, which led to his “Plum Pudding” model (Book and thinkquest- Given Source). (Picture 3)
  • Max Planck

    Max Planck
    Max Planck figured out the relationship between energy and the frequency of radiation, otherwise known as quanta (Biography). Planck concluded that all matter emits energy based off his model. (Picture 1)
  • Johan Vaaler Invented the Paperclip

  • Hantaro Nagaoka suggests the existence of nucleus; electrons move in orbits

  • Ernest Rutherford

    Ernest Rutherford
    Rutherford discovered the nucleus which he considered to be a small region of an atom with a positive charge, while the rest was empty space. During an experiment to pass alpha particles of helium through thin sheets of gold foil, he discovered that although a majority passed through the foil, some bounced off. Rutherford suggested his new atomic theory (Book). (Picture 9)
  • Neils Bohr

    Neils Bohr
    Bohr improved Ruthford’s model and discovered that electrons move in a circular orbit around the nucleus, with a specific distance (Book). (Picture 7)
  • Assassination of Archduke Franz Ferdinand of Austria (beginning of World War 1)

    (World War 1)
  • Robert Millikan

    Robert Millikan
    Based off of Thomson’s charge to mass ratio, Millikan calculated the mass of an electron. He discovered that an electron carries only one negative charge and that the mass is 1: 1840 the mass of a hydrogen atom (Book). (Picture 10)
  • Louis de Broglie

    Louis de Broglie
    Louis de Broglie proposed the idea that moving particles, like electrons, have some properties that resemble a wave. A few years later, his idea was proved to be true (Book). (Picture 12)
  • Erwin Schrodinger

    Erwin Schrodinger
    Schrodinger created the Schrodinger Equation (mathematics) that describes the radiuses of orbitals and the placement of electrons in atoms (thinkquest – Given Source). (Picture 2)
  • Werner Heisenberg

    Werner Heisenberg
    Heisenberg created the “Heisenberg uncertainty principle” that states that it’s impossible to know the velocity and the position of a particle at the same time. His observation only relates to smaller objects like electrons, but doesn’t describe objects like cars (Book).
  • James Chadwick

    James Chadwick
    Chadwick discovered the neutron by noticing that radiation of atoms wasn’t gamma radiation, but neutral. Chadwick discovered that neutrons are also located in the nucleus (thinkquest- Given Source). (Picture 5)
  • Beginning of World War 2

    (The Beginning Of World War II)