In the \"plum pudding\" model of the atom, the mass and charge of the positive p
ID: 1619240 • Letter: I
Question
In the "plum pudding" model of the atom, the mass and charge of the positive part of the atom is spread uniformly throughout its volume. If this had been correct, what would have been different about Rutherford's observations when firing alpha particles at gold foil? The alpha particles would have backscattered from the electrons instead of the nuclei. He would not have seen alpha particles bouncing backwards in the general direction of the source. The gold foil would have absorbed all of the alpha particles. Fewer of the alpha particles would have made it through the foil to the other side.Explanation / Answer
Rutherford tested "plum pudding model" by devising his "gold foil" experiment. Rutherford reasoned that if Thomson's model was correct then the mass of the atom was spread out throughout the atom. Then, if he shot high velocity alpha particles (helium nuclei) at an atom then there would be very little to deflect the alpha particles. He decided to test this with a thin film of gold atoms. As expected, most alpha particles went right through the gold foil but to his amazement a few alpha particles rebounded almost directly backwards.These deflections were not consistent with Thomson's model. Rutherford was forced to discard the Plum Pudding model and reasoned that the only way the alpha particles could be deflected backwards was if most of the mass in an atom was concentrated in a nucleus.
The correct answer is 2.
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