You are not authorized to access this page.

Atomic Theory Timeline

By rpratz
  • Democritus
    400 BCE

    Democritus

    Proposed that matter couldn't be divided into smaller pieces forever. Also claimed matter was made up of small, "hard" particles called atoms.
  • Aristotle
    340 BCE

    Aristotle

    Didn't believe in the atomic theory, actually taught different. thought that all materials on Earth were not made of atoms, but of the four elements, Earth, Fire, Water, and Air. He believed all substances were made of small amounts of these four elements of matter.
  • Lavoisier

    Lavoisier

    He wrote the first main list of elements. He also had discovered the role oxygen plays in combustion. He recognized and named oxygen (during 1778) and hydrogen (during 1783), and opposed the phlogiston
  • Dalton

    Dalton

    Created the very first atomic theory. He viewed atoms as tiny solid balls.
  • Proust

    Proust

    Proust discovered what is today called "Proust's law". This law
    stated that chemical compounds are formed of constant and defined ratios of elements, as determined by mass.
  • Faraday

    Faraday

    Faraday made one of the most significant discoveries which led to the idea of atoms having an electrical component. The particles that were first believed to be negatively charged atoms or molecules
  • Becquerel

    Becquerel

    Becquerel discovered the radioactivity in uranium. This caused scientists to change their ideas about atomic structure drastically.
  • Thomson

    Thomson

    He made the atomic model known as, "the raisin bun model". He showed the atom was made up of even smaller things.
  • Planck

    Planck

    He invented the quantum theory.
  • Marie & Pierre Curie

    Marie & Pierre Curie

    They had, "successfully isolate radioactive radium salts from the mineral pitchblende in their laboratory in Paris."
  • Einstein

    Einstein

    Einstein discovered that energy and mass are interchangeable, setting the stage for nuclear power and atomic weapons. E = MC^2
  • Millikan

    Millikan

    Millikan began a series of experiments to determine the electric charge carried by a single electron. He ended up discovering that all of the drops had charges that were simple multiples of a single number, the fundamental charge of the electron.
  • Rutherford

    Rutherford

    Discovered protons and the nucleus. He also showed that atoms have (+) particles in the center, and are mostly empty space.
  • Bohr

    Bohr

    Proposed that electrons move around the nucleus, in specific layers. Also improved Rutherford's model.
  • Chadwick

    Chadwick

    Worked with Rutherford, discovered particles have no charge. The discovery that resulted from this was the discovery of neutrons.
  • Modern Day

    Modern Day

    New modern day atomic model has electrons moving around the nucleus in a cloud. Work that has been done since 1920 has changed the model.