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Physics Plum Pudding Model and Gold Foil Experiment

The plum pudding model states that an atom is a positive sphere of 'goo' with negative electrons dotted around in it, right?

So then if a beam of alpha particles was fired at gold foil, would the positive 'goo' not repel most of the positive alpha particles? as surely if the goo was surrounding the negative charge then there wouldn't be enough electrons to deflect as there would be more positive good?

Was the outcome of the experiment just to work out the structure of the atom?

I understand that the nucleus was seen as positive as the alpha particles repelled straight back and that the surroundings must have been negative because the alpha partcielse were deflected slightly.

Im just looking for some clarity here, I'm confusing myself!
Original post by Saywhatyoumean
The plum pudding model states that an atom is a positive sphere of 'goo' with negative electrons dotted around in it, right?

So then if a beam of alpha particles was fired at gold foil, would the positive 'goo' not repel most of the positive alpha particles? as surely if the goo was surrounding the negative charge then there wouldn't be enough electrons to deflect as there would be more positive good?

Was the outcome of the experiment just to work out the structure of the atom?

I understand that the nucleus was seen as positive as the alpha particles repelled straight back and that the surroundings must have been negative because the alpha partcielse were deflected slightly.

Im just looking for some clarity here, I'm confusing myself!


I think the plum pudding model is supposed to be a cloud of positive charge with electrons scattered in it so the expected outcome of the experiment was that there would be a small scattering of alpha particles as they would only be deflected a small amount by the electrons as the alpha particles mass is much higher than an electron and the charge is spread out so would only have a little effect.

Yes the experiment was purely to investigate the structure of an atom.

The alpha particles being repelled straight back is nothing to do with charge, that shows they were hitting an object of very high (relative) mass and density. Most of the particles passed straight through showing most of an atom is empty space. Some were deflected through large angles because of the concentrated positive charge but they had to pass very close to the nucleus to show this which is why only a few were detected.

Hope this helps :smile:
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TLK
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Original post by Saywhatyoumean
The plum pudding model states that an atom is a positive sphere of 'goo' with negative electrons dotted around in it, right?

So then if a beam of alpha particles was fired at gold foil, would the positive 'goo' not repel most of the positive alpha particles? as surely if the goo was surrounding the negative charge then there wouldn't be enough electrons to deflect as there would be more positive good?

Was the outcome of the experiment just to work out the structure of the atom?

I understand that the nucleus was seen as positive as the alpha particles repelled straight back and that the surroundings must have been negative because the alpha partcielse were deflected slightly.

Im just looking for some clarity here, I'm confusing myself!


Yeah the electrons were thought to be embedded into the atom.

The atom would repel most/all of the alpha particles but they would only be deflected at a small angle since the positive charges of the atom were thought to be spread out.

I think the outcome was to test if the plum pudding model was right or not.

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