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JJ Thompson – Discovery of Electrons

Metal plate. Metal Plate. Gas-filled glass tube. Stream of negative particles (electrons). Source of Electrical Potential. JJ Thompson – Discovery of Electrons. Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 58. A Cathode Ray Tube.

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JJ Thompson – Discovery of Electrons

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  1. Metal plate Metal Plate Gas-filled glass tube Stream of negative particles (electrons) Source of Electrical Potential JJ Thompson – Discovery of Electrons Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 58

  2. A Cathode Ray Tube Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 58

  3. Thomson’s Experiment voltage source - + vacuum tube metal disks

  4. Thomson’s Experiment voltage source - + vacuum tube metal disks

  5. Thomson’s Experiment voltage source ON - OFF + Passing an electric current makes a beam appear to move from the negative to the positive end

  6. Thomson’s Experiment voltage source ON - OFF +

  7. + - Thomson’s Experiment voltage source ON - OFF + By adding an electric field… he found that the moving pieces were negative.

  8. J.J. Thomson • He proved that atoms of any element can be made to emit tiny negative particles. • From this he concluded that ALL atoms must contain these negative particles. • He knew that atoms did not have a net negative charge and so there must be balancing the negative charge. J.J. Thomson

  9. Spherical cloud of Positive charge Electrons Thomson • In 1910 proposed the Plum Pudding model • Negative electrons were embedded into a positively charged spherical cloud. Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 56

  10. Plum-Pudding Model Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 56

  11. - - - - - Thomson thought that mass was evenly distributed throughout the atom

  12. - - - - - - - - - - - - - - - - - - - - - - - - - Because, he thought the mass was evenly distributed in the atom

  13. - - - - - - - - Alpha particles Nucleus + + + + + + + + Nuclear atom Explanation of Alpha-Scattering Results Plum-pudding atom Thomson’s model Rutherford’s model

  14. The Rutherford Atom Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 323

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