Atom1

The history of the atomic theory

By obeidi
  • Democritus
    460

    Democritus

    Nothing exists except atoms and empty space; everything
    else is opinion.” - Democritus 460–370 B.C.
  • Issac Newton

    Issac Newton

    Proposed a mechanical universe with small solid masses in motion.
  • John Dalton

    John Dalton

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

    JJ Thompson

    Discovered electrons using Cathode Ray Tube experiment. He also determined the charge to mass ratio (e/m) of an electron =1.759 x 10^ 8 coulombs/gram.
  • R.A Millikan

    R.A Millikan

    He determined the charge (e=1.602 x 10 -^19 coulomb) and the mass (m = 9.11 x 10 -28 gram) of an electron in his oil drop experiment
  • Ernest Rutherford

    Ernest 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.
  • Neils Bohr

    Neils 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.
  • De Broglie

    De Broglie

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

    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

    Schrodinger

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

    James Chadwick

    Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron.