Gold foil experiment

[[Image:Rutherford gold foil experiment results.png|right|200px|thumb|Top: Expected results: alpha particles passing through the plum pudding model of the atom undisturbed.

Conclusions

The result was completely unpredicted, prompting Rutherford to later comment

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"It was almost as incredible as if you fired a fifteen-inch shell at a piece of tissue paper and it came back and hit you".

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Early in 1911 Rutherford published a revised model of the atom, known as the Rutherford atom. The observations indicated that a model of the atom with a diffuse positive charge was incorrect and that it was instead concentrated. He concluded that the atom is mostly empty space, with most of the atom's mass concentrated in a tiny centre, the nucleus and electrons being held in orbit around it by electrostatic attraction. The nucleus was around 10-15 metres in diameter, in the centre of a 10-10 metre diameter atom. Those alpha particles that had come into close proximity with the nucleus had been strongly deflected whereas the majority had passed at a relatively great distance to it.

Related Topics:
1911 - Nucleus

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Rutherford's model was developed by Niels Bohr into the Bohr model proposed in 1913. The Rutherford atom had a number of problems, in particular electrons should radiate electromagnetic energy and rapidly spiral into the nucleus.

Related Topics:
Niels Bohr - Bohr model - 1913

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The experiment failed to yield any data concerning electrons (which had to be present in order to make the atom electrically neutral). Rutherford did surmise that they would have a very small mass, and that they would be randomly distributed around the nucleus.

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