Wednesday, July 7, 2010

The Plum Pudding or the Rasin Bread Model

Joseph John "J.J." Thomson

J.J. Thomson

Until 1897, scientists believed that atoms were indivisible, but Thomson proved them wrong when he discovered that atoms contained particles known as electrons. Thomson discovered this through his explorations on the properties of cathode rays. British physicist and Nobel laureate. He is credited for the discovery of the electron and of isotopes, and the invention of the mass spectrometer.


Plum Pudding Model

The atom is composed of electrons surrounded by a soup of positive charge to balance the electrons' negative charges, like negatively charged "plums" surrounded by positively charged "pudding. Thomson's model was compared to a British dessert called plum pudding.


Experiment with Cathode Rays


First Experiment
Thomson set out to investigate whether or not he could actually separate the charge from the rays.

Second Experiment
He investigated wether or not the rays could be deflected by an electric field.

Third Experiment
Thomson measured the mass to charge ratio of the cathode rays by measuring how much they were deflected by a magnetic field and how much energy they carried.


source: wikipedia

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