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My teacher said, "Rutherford thought that all the Alpha particles would directly go through the gold foil without any collision if the plum pudding model was right. Because, as said in plum pudding model, positive charges are arranged in a balanced way in the atom with electrons like plum in pudding. As there is no densely accumulated charge in the center, so the Alpha particle will not deviate by anything." But two question raised on my mind.

  1. Is my teacher right?
  2. If not, then why?
  3. If yes, then why evenly accumulated positive charge will not deviate the Alpha rays? I mean, when the alpha ray will come near to the pudding like positive charges, it should deviate more sooner nah? Moreover, as there are evenly arranged positive charges, so, no empty space is in the atom. So, no alpha particles would come across the foil. Is my assumption true if thought from plum pudding model?
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    $\begingroup$ A plum pudding model prediction would be like results of shooting bullets through a wall formed from dust bound by polyurethane foam. But the experiment results were like if there were occational stones and not all dust in that shooted at wall. $\endgroup$
    – Poutnik
    Feb 17, 2021 at 14:13
  • $\begingroup$ @Poutnik as a high school student, don't have much idea about polyurethane foam but understood the main theme! Thanks $\endgroup$ Feb 17, 2021 at 14:46
  • $\begingroup$ chemistry.stackexchange.com/questions/45115/… And other questions are pretty similar. $\endgroup$
    – Jon Custer
    Feb 17, 2021 at 14:49
  • $\begingroup$ It is a very common foam, used e.g. for sponges or padding of products in shipping boxes. We use in Czech a generic name molitan, but I was not sure about what is used in English. See wikipedia polyurethane $\endgroup$
    – Poutnik
    Feb 17, 2021 at 14:50
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    $\begingroup$ Details, details. It isn't that there would be no repulsion in the plumb pudding model, it is that the repulsion would be very different. A large, diffuse mass of positive charge might bend the beam slightly, but would not cause large deviations. But a tiny, hard nucleus could occasionally cause big deviations. $\endgroup$
    – matt_black
    Feb 17, 2021 at 16:56

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First of all, yes, your teacher is right for most of the part but it is not that they will go without any collision. Instead, they will penetrate through the foil like a bullet shot at paper.

It is not that the alpha rays will not be deviated but that if the charge was evenly spread throughout the atom, it would not be able to provide sufficient repulsive forces to wear out the kinetic energy already given to the alpha particles and slow them down. As a result, the alpha particles should have penetrated the atom like a bullet penetrates a sheet of paper.

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