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Rutherford’s experiment. Day 2. Last time. Discussion of early atomic model- the plum pudding model To refresh your memory: Large slightly positive mass with tiny negative electrons in it. Deconstructing Thomson’s model. You have A source of alpha particles (positively charged)
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Rutherford’s experiment Day 2
Last time • Discussion of early atomic model- the plum pudding model • To refresh your memory: • Large slightly positive mass with tiny negative electrons in it
Deconstructing Thomson’s model • You have • A source of alpha particles (positively charged) • Some atoms of the same element (identical) • Detection device (to see where your alpha particles went) • How would you test Thomson’s model?
Overview of the gold-foil experiment • Hans Geiger and Ernest Marsden shot helium nuclei (alpha particles, +2 charge) at a very thin sheet of gold foil • What do you think would happen, based on the plum pudding model?
Rutherford’s experiment- online • http://phet.colorado.edu/en/simulation/rutherford-scattering • Make sure to click “show traces”
1) What effect does alpha particle speed have on repulsion? • 2) What does the size of the neutron have on repulsion? • 3) How does the relative proportion of protons to neutrons affect repulsion?
Rutherford’s conclusions • How did this experiment change perceptions of what an atom is? • There is a nucleus with a positive charge (since the + charge must be concentrated) • Most of the atom is empty space!