The Histpry Of The Atom

By kaylamarie08
  • 465 BCE

    Democritus

    Democritus
    According to Democritus atoms were miniscule quantities of matter. Democritus hypothesized that atoms cannot be destroyed, differ in size, shape and temperature, are always moving, and are invisible. He believed that there are an infinite number of atoms.

  • John Dalton

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

  • William Thomson

    William Thomson
    Used a CRT to experimentally determine the charge to mass ratio of an electron =1.759 x 10 8 coulombs/gram.

  • 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.

  • Niels Bohr

    Niels Bohr
    proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities