# Exploring the Alpha Particle-Electron Interaction in Gold Foil Experiments

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• tbn032
In summary: I am unable to understand how is the mass of electron instead of charge (alpha particle has 3.2x10^-19C charge and gold foil has 79 electrons each having -1.6x10^19C charge)relevant in deciding whether it will deflect the alpha particle. The reason around this is given that alpha particle will push through the electron and hence it will not get deflected. How does it exactly matter that the mass of electron is significantly less than electron, the electrostatic forces between the electrons and alpha particle would be the same regardless of mass.I don't understand the question.
tbn032
My current understanding:

The mass of alpha particle is approximately 7340.6 times higher than the mass of electron.in the gold foil scattering experiment the deflection of alpha particle due to electron is approximately zero.
The reason that is given is that since the electron is much lighter than the alpha particle, it is unable to deflect the alpha particle and the electron itself get scatted instead of deflecting the alpha particle.

My questions are:

1)How can the electron be pushed or scattered by the alpha particle when the electron is revolving in its orbit around the nucleus, and when the electron is bound to the nucleus?

2)I am unable to understand how is the mass of electron instead of charge (alpha particle has 3.2x10^-19C charge and gold foil has 79 electrons each having -1.6x10^19C charge)relevant in deciding whether it will deflect the alpha particle. The reason around this is given that alpha particle will push through the electron and hence it will not get deflected. How does it exactly matter that the mass of electron is significantly less than electron, the electrostatic forces between the electrons and alpha particle would be the same regardless of mass.

If you fire a cannonball at a pea then the pea gets scattered and the cannonball will hardly change direction.

You can see the effect of mass qualitatively by studying particle collisions and using energy and momentum conservation. Mass affects both these quantities. Momentum is ##m\vec v## and all that.

tbn032 said:
My current understanding
The mass of alpha particle is approximately 7340.6 times higher than the mass of electron.in the gold foil scattering experiment the deflection of alpha particle due to electron is approximately zero.
The reason that is given is that since the electron is much lighter than the alpha particle, it is unable to deflect the alpha particle and the electron itself get scatted instead of deflecting the alpha particle.
My questions are.
1)How can the electron be pushed or scattered by the alpha particle when the electron is revolving in its orbit around the nucleus, and when the electron is bound to the nucleus?
The answer to this is more subtle. There is a probability that the alpha particle interacts with the electron. You need QM to get the fully story. The energy of the alpha particle must be sufficient to unbind the electron from the nucleus. A cannonball could take your head off!
tbn032 said:
How does it exactly matter that the mass of electron is significantly less than electron, the electrostatic forces between the electrons and alpha particle would be the same regardless of mass.
Newton's second law ##F = ma##. Same force for the same duration accelerates a small particle more than a large one.

tbn032 said:
How does it exactly matter that the mass of electron is significantly less than electron, the electrostatic forces between the electrons and alpha particle would be the same regardless of mass.
If you’re thinking classically, there is an electrostatic force on the electron from the alpha because they are both charged, and there is an equal and opposite force on the alpha from the electron (by Newton’s third law). But the alpha is far more massive, so the same force moves it much less - basically the electron gets shoved out of the way without appreciably changing the path of the alpha.

Be aware though that there is only so far you can push that classical model. We now know from quantum mechanics that electrons aren’t small solid objects orbiting the nucleus. It’s better (still not right, for that we need quantum electrodynamics with its fairly daunting mathematical price of admission) to think of the electrons as a sort of cloud around the nucleus that no more deflects the alpha than a cloud in the sky deflects a bullet.

Nugatory said:
think of the electrons as a sort of cloud around the nucleus
Also, the total charge (79+) of the gold nucleus could be thought of as a replulsive force which would perhaps yield a smaller measured diameter of that nucleus.

## 1. What is the purpose of exploring the alpha particle-electron interaction in gold foil experiments?

The purpose of these experiments is to understand the structure of atoms and the behavior of subatomic particles, specifically the interaction between alpha particles and electrons. This was a significant discovery in the field of nuclear physics and helped pave the way for further research and advancements in our understanding of the atomic world.

## 2. How were gold foil experiments conducted?

In these experiments, a beam of alpha particles was directed at a thin sheet of gold foil. The alpha particles were emitted from a radioactive source and passed through a small hole in a lead barrier before hitting the gold foil. The particles were then detected on a fluorescent screen placed behind the foil.

## 3. What were the results of the gold foil experiments?

The results of these experiments showed that most of the alpha particles passed straight through the gold foil, but a small percentage were deflected at large angles or even bounced back. This led to the discovery of the atomic nucleus and the understanding that atoms are mostly empty space with a dense, positively charged nucleus at the center.

## 4. How did the gold foil experiments contribute to the development of the atomic model?

The gold foil experiments provided evidence for the existence of the atomic nucleus and disproved the previously accepted plum pudding model of the atom. This led to the development of the Rutherford model, which described the atom as a small, positively charged nucleus surrounded by orbiting electrons.

## 5. What impact did the gold foil experiments have on the field of science?

The gold foil experiments were a crucial step in understanding the structure of atoms and paved the way for further research and advancements in the field of nuclear physics. This discovery also had a significant impact on other areas of science, such as chemistry and materials science, as it provided a better understanding of the fundamental building blocks of matter.

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