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Atomic Theory Through the Ages

By HusseyGabrielle
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    Democrius

    Democrius
    Democritus was the first person to suggest that matter couldn't be divided (Democritus lived in 460-370 BC). He fabricated the term "atomos". It means tiny particles that make up matter and move around in empty space.
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    Aristotle

    Aristotle
    (Aristotle was alive 384-322 BC.) Aristotle disagreed Democritus' ideas that atoms moved through empty space. He completely denied the existence of atoms. People believed Aristotle's idea more than Democritus.

  • John Dalton

    John Dalton
    Dalton took Democritus ideas and revised them. He revived the term "atom" and he believed “Atoms are the smallest particles of matter and are indivisible and indestructible.” He explained his theory proves the Law of Conversation of Mass. "Atoms can be rearranged, separated, or combined to form new things, but cannot be created, destroyed, or divided in the process.”

  • J.J. Thompson

    J.J. Thompson
    Physicist J.J. Thompson designed experiments to determine the ratio of the particle’s charge to its mass. Concluded that the mass of the particle was much less than the Hydrogen atom, which did not agree with Dalton’s theory. He was awarded (1906) for the discovery of the electron.

  • Robert Millikan

    Robert Millikan
    Robert Millikan designed an oil drop apparatus to determine the charge of the electron. The charge was equal to a single unit of negative charge which makes the charge -1. He proposed the plum pudding model.

  • Ernest Rutherford

    Ernest Rutherford
    He designed an experiment to see if α-particles would be deflected off of foil. He expected the all of the α-particles to pass right through the gold foil, but a few bounced back in strange angles. Rutherford learned that Thomson’s plum pudding model was incorrect. There had to be a place for the positive charge and most of the mass to stay. He said that it was contained in a small region in the center of the atom and he called that spot the nucleous. He conculded protons exsist.

  • James Chadwick

    James Chadwick
    Chadwick deminstrated that the nucleous had another netural subatomic particle, the neutron. It has no electric charge. He won an award for the discovery of the neutron.