The Evolution of the Atom Model

By scauron
  • 400 BCE

    Democritus

    Democritus
    From ancient Greece, Democritus created the idea of the atom, making the foundation for others to come. He believed that all matter was made of atoms, which were indestructible and varied in size and shape.
  • 400 BCE

    Democritus' Model of the Atom

    Democritus' Model of the Atom
    The model Democritus came up with was a sphere.

  • John Dalton

    John Dalton
    Born in Eaglesfield, England, Dalton continued with the idea of the atom, using prior knowledge to come up with these ideas:
    Matter is made of atoms, which are indivisible.
    All atoms of one element have the same mass and properties.
    Compounds are combinations of different kinds of atoms.
    A chemical reaction is atoms being rearranged.

  • John Dalton's Model of the Atom

    John Dalton's Model of the Atom
    Dalton's model of the atom was a sphere.

  • J.J. Thompson

    J.J. Thompson
    Born in Cheetham Hill, England, J.J. Thompson discovered the electron through experimentation.

  • J.J. Thompson's Atom Model

    J.J. Thompson's Atom Model
    This model is called the Plum Pudding model. It shows electrons floating in an area of positivity.

  • J.J. Thompson's Experiments

    J.J. Thompson's Experiments
    Thompson experimented with cathode ray tubes. When high voltage is sent across the cathodes at the end of a cathode ray tube, a beam of particles goes from the cathode to the anode. Thompson put two oppositely charged electric plates around the cathode ray, which deflected away from the negatively charged plate and towards the positively charged one. This showed that the particles, electrons, were negatively charged.

  • Ernest Rutherford

    Ernest Rutherford
    Born in Nelson, New Zealand, Ernest Rutherford discovered the nucleus.

  • Ernest Rutherford's Atom Model

    Ernest Rutherford's Atom Model
    Rutherford's atomic model showed a small nucleus surrounded by empty space.

  • Ernest Rutherford's Experiments

    Ernest Rutherford's Experiments
    Rutherford fired a beam of alpha particles at a gold sheet. He put radium in a lead box with a pinhole. The lead absorbed most of the radiation but a small beam of particles went out the keyhole towards the foil. A few alpha particles were deflected from their path. This showed that the positive charge must only be in a small part of the atom, and the rest is empty space.

  • Bohr Model

    Bohr Model
    This model showed electrons moving in orbits called energy levels around the nucleus.

  • Niels Bohr

    Niels Bohr
    Born in Copenhagen, Bohr improved the atom model even further. In 1922, he won the Nobel Prize for this work. He was the head of Theoretical Physics at Copenhagen University for forty years, from 1920 to his death.

  • Quantum Mechanical Model

    Quantum Mechanical Model
    This model shows the probability of the position of an electron by showing a nucleus surrounded by an electron cloud. The electron cloud shows where electrons might be found.

  • Erwin Schrödinger

    Erwin Schrödinger
    Schrödinger updated the model of the atom by creating the Quantum Mechanical Model. He also spent time learning about many other subjects such as Italian painting and botany. In World War I, he was an artillery officer.