Atomic Theory

By tqnua
  • 400 BCE

    Democritus

    Democritus
    The Greek philosopher Democritus was the first to come up with the idea of atoms, at the time he called them "atomos." He beleived that atoms were small invisible particles that came in different shapes and sizes. His idea was rejected and ignored for the nest 2,000 or so years.
  • Period: 400 BCE to

    Scientists timeline

  • John Dalton

    John Dalton
    John Dalton came up with evidence to prove Democritus' theory. His four points are that matter is composed of atoms, atoms of the same element are identical, and the ones of different element are not, atoms form compounds, and chemical reactions are a rearrangement of atoms.

  • J.J Thomson

    J.J Thomson
    Thomson experimented with cathode ray tubes and found out that the cathode ray deflected away from the negatively charged plate and towards the positively charged plate. Cathode ray particles were called electrons, and there are also smaller particles called elements: this disproved that atoms are not divisible. He made a model people call today the "Chocolate Chip Cookie Model"

  • Ernest Rutherford

    Ernest Rutherford
    Rutherford experimented using gold foil and alpha particles, a lot of the particles weren't deflected off of the foil, a few bounced off, and some redirected back but most just passed through. Through this experiment he concluded that there was empty space, so the mass of the atom must be in a small space called the nucleus. His model is known as The Necleur Model where electrons are around the nucleus and protons and neutrons are inside of it

  • Niels Bohr

    Niels Bohr
    Bohr realized that the atom would be unstable in Rutherford's model, so he modified it by saying that the electrons on the outside moved in an orbit around the nucleus. He explained that electrons would jump from one orbit to another by controlling its energy and the lost energy is a form of light which is a unique color for every element. Bohr's model is called the Planetary model.

  • Erwin Schrodinger

    Erwin Schrodinger
    Schrodinger realized that it isn't possible to know the specific location of the electrons within the atom, and the location most likely could only be found through probability. He thinks that electrons could be found in things called clouds / orbitals. The orbitals don't look like the energy shells that Bohr came up with.