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Atomic Theory Through the Years

  • Period: 460 BCE to 370 BCE


    Democritus is born.
  • 400 BCE

    Atomos - Democritus

    Atomos - Democritus
    Democritus discovered that if you were to cut something into small pieces, eventually it wouldn't be able to be cut. Democritus called this an "atomos". Democritus also believed that atomos came in different size & shape.
  • Period: to

    John Dalton

    John Dalton is born.
  • Atoms - John Dalton

    Atoms - John Dalton
    Different from Democritus, Dalton was able to get evidence that supported his atomic theory. He had the same theory as Democritus where small indivisible pieces of matter are called atoms. Dalton discovered that chemical reactions are just different arrangements of atoms.
  • Period: to

    JJ Thomson

    JJ Thomson is born.
  • Electron - JJ Thomson

    Electron - JJ Thomson
    JJ Thomson experimented with cathode ray tubes. These were glass tubes in which most of the air inside was evacuated. He experimented by putting through voltages to the tube. This caused his experiments to conclude with that the tube was negatively-charged. JJ Thomson also made the plum pudding model. Which is were positive charge is like the pool, and the electrons are like little things around the pool.
  • Period: to


    Rutherford is born.
  • Period: to


    Bohr is born!
  • Period: to


    Schrodinger is born.
  • Rutherford's Atomic Model

    Rutherford's Atomic Model
    In the center of Rutherford's Atomic model is a type of naturally radioactive particle, they are positively charged particles with the mass of about 400 times more than hydrogen atom. And for the electrons, they are cloud and they are swarming around the positively charged nucleus.
  • Bohr's Atomic Model

    Bohr's Atomic Model
    Different to Rutherford's model, electrons move in stable and even orbits. They do not spiral in and destroy the atom. The energy can depend on how the electron is. He also discovered that electrons could move from orbits when excited/energized, that is called quanta.
  • Schrodinger's Atomic Theory (Modern Theory)

    Schrodinger's Atomic Theory (Modern Theory)
    Schrodinger found that the location of the electrons could only be identified by the probability of finding them in an area around the nucleus. Those areas are called electron clouds. Every level of electron clouds had different shapes and corresponded to the energy of the electron. So, the main idea is: Bohr's model was not exactly correct but is still useful. Finally, electrons move in probability in electron clouds.