Atomic Theories

  • John Dalton

    John Dalton
    John Dalton was an English chemist that transformed Democritus's ideas on atoms into a scientific theory. He studied the ratios in which elements combine in chemcial reactions. Dalton came up with theories to explain the observations that he had in his expiraments in 1803. This is how Dalton's atomic theory was created. The theory states that elements are composed of identical indivisable atoms. Multiple atoms can become mixtures and compounds but one cannot change into a different atom.
  • J.J. Thomson

    J.J. Thomson
    J.J. Thomson, an English physicsist discovered the electron and determined the charge-to-mass ratio of an electron. He passed electric current through glass tubes sealed with gas. A source of electricity was connected to the electrodes of which one had a positive charge and one had a negative charge he soon had an attraction and created the cathode ray. Then he deflected it with a magnet.
  • Mary and Pierre Curie

    Mary and Pierre Curie
  • Ernest Rutherford

    Ernest Rutherford
    He discovered the atomic nucleus. He did this by shooting a beam of tiny positively charged particles at thin metal foils. The major deflections were caused by the alpha particles being repelled by something small, dense, and positive inside the atoms of the foil. Thus he created the atomic nucleus.
  • Robert A. Milikan

    Robert A. Milikan
    Milikan was a U.S. physicist who found the charge carried by an electron. Using this and the ratio found by Thomson, he found the mass of an electron. He balanced the downward gravitational force and the upward charge on tiny drops of oil that were suspended between two metal electrodes.
  • Niels Bohr

    Niels Bohr
    Bohr proposed that the electron moves in a circular orbit at fixed distances from the nucleus.
  • Louis de Broglie

    Louis de Broglie
    French physicist Louis de Broglie suggests that moving properties lik electrons have properties of waves. After a few yaers experimental evidence supports the hypothesis,
  • Erwin Schrödinger

    Erwin Schrödinger
    He develops mathematic equations to describe the motion of electron in atoms which leads to the electron cloud model.
  • James Chadwick

    James Chadwick
    The English physicist confirms the existence of charge-less neutrons. The belief is that nuclei contain neutrons and positively charged protons.