Atomic Theory

  • Democritus

    Democritus
    Democritus - 442 BC
    Postulated the theory of atoms and void; the universe is made
    up of empty space and a nearly infinite number or invisible
    particles differing in arrangement, form, and position. He
    stated that all all matter is composed of indivisible atoms
  • John Dalton

    John Dalton
    English chemist who proposed the Atomic Theory which
    stated that all matter was composed of small indivisible
    particles called atoms. These atoms possess unique
    characteristics and weight for different elembets.
    He also stated that three types of atoms exist: simple
    (elements), compound (simple molecules), and complex
    (complex molecules).
  • J.J Thomson

    J.J Thomson
    1998 First to measure the electron. Developed the
    plum-pudding model of the atom. Describes the atom as a
    slightly positive sphere with small electrons inside.
  • Ernest Rutherford

    Ernest Rutherford
    1909-1911
    Inferred a small, dense, positively-charged nucleus as the
    result of the alpha particle scattering gold foil experiment.
  • Niels Bohr

    Niels Bohr
    1913
    A Danish physicist who stated that electrons could only
    orbit the nucleus in succesively larger orbits around the
    nucleus. The outer orbits could hold more electrons. The
    electrons in the outermost shell determine the properties of
    the atom. He also inferred that when an electron moves from
    an outer orbit to an inner orbit it emits a quantum of energy,
    a photon, in the form of light.
  • Erwin Schrodinger

    Erwin Schrodinger
    1926
    Developed wave mechanics which describe the behavior
    of quantum systems for bosons.