The heavy, dense nucleus of the atom caused the alpha particles to bounce back in Rutherford's experiment.
The part of a atom that causes particles to bounce back is the electron cloud. However, there are some things that are able to pass through it.
The alpha particles beam is scattered.
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Before we state the results of the Rutherford gold foil experiment based on the correctness of the Thomson plum pudding model, let's back up and review just a bit. Atoms were thought to be made up of electrons distributed in a positive "matrix" of sorts. With the electrons "evenly distributed" throughout the volume of the atom, a parallel or comparison was made to plum pudding. The plums, which were "scattered" throughout the pudding, were thought of as the electrons in the atom. This is the basis for the plum pudding model of the atom. The gold foil experiment that Rutherford proposed was set up, and alpha particles were "fired" at gold foil from an alpha source (alpha emitter). As the alpha particles were known to be massive compared to an electron, an experiment on atoms conforming to the plum pudding model of the atom would show that the alpha particles zip right through. There would be nothing anywhere near as massive as an alpha particle in the plum pudding atom to stop or scatter them. All the alpha particles would strike the target screen behind the foil in a direct line from the source. When the experiment was actually conducted, most of the alpha particles struck as expected. But a few were scattered in different directions, and this was "impossible" if the atom was constructed as suggested by the plum pudding model. What internal structure in the plum pudding atom could possibly deflect (scatter) a few (or any!) alpha particles? The plum pudding model was set aside, and Rutherford's suggestion was that most of the mass of the atom was concentrated as a positive charge in the center in what we call a nucleus.
In a solid particles vibrate and stay in one spot, however due to vibrating, they may move slightly. In liquids, they bounce around in a small area relitvly close to their "spot". In a gas, particles bounce around freely, moving around all of the given space. To relate , a solid's particles are like vibrating cell phone, staying in place. However gas's are like bouncy ball enclosed in a jar
The heavy, dense nucleus of the atom caused the alpha particles to bounce back in Rutherford's experiment.
Rutherford fired alpha particles at a sheet of atoms in order to determine the atomic structure. The alpha particle is positively charged. Those particles that bounce straight back are the ones that hit the nucleus of the atom and were repelled by the nucleus's positive charge.
No, they struck the nucleus of the atom. Since the alpha particles are positively charged and nucleus is positively charged as well, they repelled each other and alpha particles are repelled back
Alpha particles are composed of two neutrons and two protons, so they have a positive charge. When the alpha particles bounced straight back from the gold foil, this indicated that they had hit a particle of like charge, in other words a positively charged particle in the gold foil, which repelled the alpha particle.
The alpha particles beam is scattered.
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In conclusion... Rutherford's experiment involved a radioactive source emitting alpha particles (2 protons and 2 neutrons). The radioactive source was aimed at a thin sheet of gold. The main observation made was that a few alpha particles were repelled back the way they had come, and this was not expected. This was because the positively charged alpha particles (2 protons), by the laws of electrostatic repulsion, were repelled by the positively charged nucleus of the atoms in the gold. He then made the final conclusion of that the small nucleus of an atom is central, has a large mass and positive charge. So yes, the nucleus is small compared to the size of an atom, however it was mainly the fact that there is one concentration of positive charge (nucleus) in the atom that repelled the alpha particles that helped Rutherford to show the structure of an atom.
The sensors in the back of your eyes detect light particles that bounce off the thing you're looking at.
If the alpha particles hit the gold foil most of the alpha particles will pass through the gold foil because atoms mostly consists of empty space and some alpha particles will be deflected including a very small number of alpha particles will bounce back in the direction they came from because the atom has a very small positively charged mass called the nucleus.
They stop.