Atomic Theory Time Line Project

  • Aristotle
    340

    Aristotle

    There are 5 elements in matter: air, earth, water, fire, and Aether.
  • Democritus
    460

    Democritus

    Democritus adopted the atomic theory. The atomic theory asserted that the universe is composed of two elements, the atoms and the void in which they exist and move.
  • Antoine Lavoisier

    Antoine Lavoisier

    Determined the Law of Conservation of Matter by extensive experimentation.
  • Joseph Louis Proust

    Joseph Louis Proust

    Detemined the law of constant composition.
  • John Dalton

    John Dalton

    formulated an atomic theory of matter with 4 postulates, whcin were: 1. Elements are composted of small particles called atoms.
    2. All atoms of a given element are identical. 3. Atoms are neither created nor destroyed in chemical reactions. 4. Compounds always contain the same proportion of elements.
  • Henri Becquerel

    Henri Becquerel

    Henri Becquerel discovered some chemicals spontaneousely decompose and give off pentrating rays while studying the effect of x-rays on photographic film.
  • J.J. Thomson

    J.J. Thomson

    J.J. Thomson performed a CRT experiment and determined that the ray was composed of negative particles, called electrons. He determined the mass-charge ratio for an electron and came up with the "plum pudding" model of the atom .
  • Marie and Pierre Curie

    Marie and Pierre Curie

    Discovered two radioactive elements, polonium and radium.
  • Ernest Rutherford

    Ernest Rutherford

    He performed the gold foil experiment, determined that atoms contained a very small, positively charged core at the center, called this core the nucleus and came up with the nuclear model of the atom with electrons orbiting around the nucleus.
  • Max Planck

    Max Planck

    Max used the idea of quanta (discrete units of energy) to explain hot glowing matter.
  • Robert Millikan

    Robert Millikan

    He performed an "oil-drop" experiment, determined the charge of one electron and using the known mass-charge ratio, was able to calculate the mass on one electron (9.11x10^-28g).
  • Niels Bohr

    Niels Bohr

    Developed the quantized orbit model of the atom and discovered that electrons can only reside in certain energy levels.
  • Louis de Broglie

    Louis de Broglie

    De Broglie discovered that electrons had a dual nature-similar to both particles and waves (particle/wave duality). He supported Einstein’s ideas.
  • Erwin Schroedinger

    Erwin Schroedinger

    Expanded the idea that electrons behaved as particles and waves, this developed the quantum mechanical model of the atom
  • James Chadwick

    James Chadwick

    The neutron was discovered using alpha particles which discovered a neutral atomic particle with a mass close to a proton.
  • Glenn Seaborg

    Glenn Seaborg

    Glenn Seaborg synthesized 6 transuranium elements and suggested a change in the layout of the periodic table.
  • Michael Faraday

    Michael Faraday

    Faraday coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis. He himself was not a proponent of atomism and he studied the effect of electricity on solutions.
  • Albert Einstein

    Albert Einstein

    Einstein published the famous equation E=mc 2. Also he proved that atoms actually exist.
  • Lise Meitner

    Lise Meitner

    Lise conducted experiments verifying that heavy elements capture neutrons and form unstable products which undergo fission. This process ejects more neutrons continuing the fission chain reaction.
  • Otto Hahn

    Otto Hahn

    Otto Hahn discovered fission in the nucleus of an atom.
  • Indivisible solid sphere model

    Democritus' theory, atom is the smallest particle of natter
  • Plum Pudding Model

    Plum Pudding Model

    Thomson's idea that protons and electrons were contained in the nucleus.
  • Planetary Model

    Planetary Model

    The idea that electrons move around the nucleurs.
  • Electron Cloud Model

    Electron Cloud Model

    The idea that electrons surrounded the nucleus.
  • Quantum Mechanical Model

    Max Planck's idea that electrons circled the nucleus in levels.