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JJ. Thomson (1856-1940)
- Studied the Cathode Ray Tube
- Found the mass to charge ratio of an electron
- Led to the Plum Pudding Model
English Physicist
Discovered the Electron
The Design of the Cathode Ray Tube
So! Thompson has discovered the electron, and it must live inside atoms.
It is much less massive than the the atom itself, so perhaps we have little electrons stuffed into the ‘rest’ of the atom like raisins in the oatmeal, or:
Plum Pudding...
Robert Milliken (1868-1953)
– Measured minimum electric charge that could be carried by a particle (1905)
– This was the charge of the electron
– Enabled him to find the mass of the electron
American Physicist
Performed the Oil Drop Experiment
Millikan’s Oil Drop Experiment
Used To Determine the Charge of an Electron
Ernest Rutherford (1871-1953)
• New Zealand born physicist
• Worked with nuclear radiation
• Performed the Gold Foil Experiment
• Discovered the nucleus (1910)
• Discovered the proton (1918)
The Gold Foil Experiment
Demonstrated that the atom contains a nucleus which is:
a. Very tiny – most of the particles missedb. Positively charged – some were deflectedc. Very dense – some bounced off
James Chadwick (1891-1974)
• Discovered the neutron in 1932
• In college he stood in the wrong line.
He wanted to be a mathematician, but was in the line for physics and was too embarrassed to switch.
• Instead he became a famous physicist.
End!
The story’s not over, but we’ll pick it up in chapter 4.