History Of the Atom

By Cgonzales

  • Democritus (Actually Happened in 403 BC)

    Came up with the theroy that "the universe is composed of two elements: the atom and the void in which they exist and move

  • Lavosier

    Proposed the conservation of matter theory

  • Dalton

    Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass.

  • Thompson

    Used a CRT to experimentally determine the charge to mass ratio (e/m) of an electron =1.759 x 10 8 coulombs/gram. Hear Thompson talk about the size of an atom. Examine Thompson's 3 experiments to verify atoms Parts. he also Studied "canal rays" and found they were associated with the proton H + .

  • Rutherford

    Studied radiations emitted from uranium and named them alpha and beta.He estimated atom size and concluded mass was concentrated in the nucleus.

  • Curie

    Studied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium and radium

  • Planck

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

  • Einstien

    Formulated the special theory of relitivity

  • Millikan

    Oil drop experiment determined the charge (e=1.602 x 10 -19 coulomb) and the mass (m = 9.11 x 10 -28 gram) of an electron.

  • Rutherford

    Using alpha particles as atomic bullets, probed the atoms in a piece of thin (0.00006 cm) gold foil . He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus.

  • Bohr

    Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of sucessive orbital shells of electrons.

  • Broglie

    Discovered that electrons had a dual nature-similar to both particles and waves. Particle/wave duality.

  • Heisenberg

    Described atoms by means of formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminancy - you can not know both the position and velocity of a particle.

  • Schrodinger

    Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom.

  • Chadwick

    Using alpha particles discovered a neutral atomic particle with a mass close to a proton. This lead to the discovering of the neutron.