![]() Millikan used his apparatus to make many measurements of the effect of the electric field vs. ![]() Thus there are obviously particles smaller than atoms. Using the smallest charge obtained and Thomson's charge/mass ratio the electron mass is roughly 1/2000 the mass of the lightest atom. In 1909 Robert Millikan used the classic oil drop experiment to determine the charge on these particles. He was able to measure the charge/mass ratio of these particles and found this to be the same regardless of what gas was in the tube or what metal the electrodes were made from. Thomson demonstrated in 1897 that the rays consist of a stream of negatively charged particles which he called electrons. From careful experiments with cathode ray tubes J.J. Thus these tubes have been called cathode ray tubes. Thomson (seen here in his lab with one of his many hand-made cathode ray tubes)Īssociated with the flow of electricity in such a tube are rays which originate from the negative electrode-the cathode. The first evidence for sub-atomic particles came from experiments with the conduction of electricity through gases in sealed glass tubes at low pressures.įigure : J.J. An eminent organic chemist of the time, Adolf Kolbe, said in 1877, "Dalton's atoms are no more than stupid re table-tapping and supernatural explanations." Some contemporaries of Dalton remained unimpressed.
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