Ernest Rutherford (1871 - 1937)
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Current Atomic Model 
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- Discovered the proton in 1910, giving us a new model of
the atom which has small, hard, positively charged protons in a nucleus. He
and other scientists weren't sure where the electrons fit into this structure
so they are depicted above as just floating around somewhere outside the nucleus.
- Remember, before this time we were working with the Plum Pudding model of
the atom. Which involved hard electrons floating in a mush of positive charge.
- Rutherford decided to test this model by setting up what is now known as
the Gold Foil Experiment. This involved bombarding a very thin sheet of gold
foil with positively charged alpha particles. Given the Plum Pudding model,
Rutherford expected all of the alpha particles to blast their way through
the haze of positive charge that was theorized in that model of the atom.
What Rutherford found was that almost every alpha particle did go straight
through the foil. However, a few particles were deflected to the side and
1 of every 20,000 was deflected back. Click
here to see a recreation of the Gold Foil Experiment.
- From this experiment Rutherford determined the following.
- There is a nucleus. Why?
- The nucleus is very small. Why?
- The nucleus is very dense. Why?
- The nucleus is positively charged. Why?
Click here
to see a video clip explaining why he thought the nucleus was positively
charged instead of neutral.
- So we have a new model of the atom with protons in a very small (1/10,000
the size of the total atom), dense, nucleus, and electrons doing something
somewhere, perhaps orbiting, perhaps not.
