Atomic Theory Timeline

  • 400 BCE


    The first scientist that used the word atom which means indivisible
    Democritus believed the atom was - the smallest particle of matter. Case closed. Makes sense if you stop and think about it. He was already talking about tiny invisible things, and there was no technology available to him that would allow him to see the atom.
    Democritus's model was of course and atom and which he thought was the smallest existing matter.
  • Antione Lavoisier

    Antione Lavoisier
    Antoine Lavoisier, a French chemist known as "the father of modern chemistry", mainly discovered the role of oxygen in combustion and respiration, proved the law of conservation, reformed the chemical nomenclature, and named hydrogen.
  • John Dalton

    John Dalton
    Dalton spent a lot of time in his lab observing various chemical reactions. Dalton advanced atomic theory was by saying we had many different atoms out there. His model, often dubbed the "billiard ball" model, basically says you can't divide the atom into smaller pieces.
  • J.J Thompson

    J.J Thompson
    Thompson is credited with discovering the electron! By this time along our timeline, the science community had accepted the idea of atoms. Thompson's model basically says that atoms are spheres (cookies), which have an overall, diffuse positive charge (the cookie dough) with little negative electrons (chips) randomly appearing throughout.
  • Robert Millikan

    Robert Millikan
    Robert Millikan was a physicist who discovered the elementary charge of an electron using the oil-drop experiment.
  • Ernest Rutherford

    Ernest Rutherford
    Rutherford discovered the nucleus of the atom, and he was as surprised by the discovery as anyone! His model was With proof that positive charges were centralized in atoms, Rutherford refined J.J. Thompson's model. Instead of showing a diffuse overall positive charge, Rutherford showed all of the positive charges held in a nucleus.
  • Niels Bohr

    Niels Bohr
    Bohr's contribution to the atomic structure wasn't as dependent on a specific experiment as it was on a deep understanding of attraction and killer math skills.
    In the solar system, Bohr reasoned, planets are kept in line by gravity.
  • Eugene Goldstein

    Eugene Goldstein
    Eugene Goldstein discovered positive particles by using a tube filled with hydrogen gas (this tube was similar to Thomson's tube). This resulted in The positive particle had a charge equal and opposite to the electron. The positive particle was named the proton.
  • Henri Becquerel

    Henri Becquerel
    The becquerel is the unit of radioactivity in the International System of Units. becquerel; is known for his discovery of spontaneous radioactivity.
  • Max Planck

    Max Planck
    Max Planck was a German theoretical physicist who discovered the quantum of action, now known as Planck's constant, h, in 1900. This work laid the foundation for quantum theory, which won him the Nobel Prize for Physics in 1918.
  • Louis De Broglie

    Louis De Broglie
    In 1924 Louis de Broglie introduced the idea that particles, such as electrons, could be described not only as particles but also as waves. This was substantiated by the way streams of electrons were reflected against crystals and spread through thin metal foils.
  • Werner Heisenberg

    Werner Heisenberg
    Heisenberg's name will always be associated with his theory of quantum mechanics, published in 1925, when he was only 23 years old. For this theory and the applications of it which resulted especially in the discovery of allotropic forms of hydrogen, Heisenberg was awarded the Nobel Prize for Physics for 1932.