Rutherford Scattering Simulation Worksheet

Unit V: Rutherford Scattering - (PhET Interactive Simulations) Rutherford’s Gold Foil Experiment Part 1: Rutherford Atom Before beginning this exercise, be sure you have read in the text about Rutherford's Gold Foil experiment. This will help in your understanding of what is happening in this simulation (section 2.2, page 49). Once ready & with the simulation open, review the legend in the upper right so you have an understanding of what is being shown in this simulation. 1. Set the number of protons to 20 (lower right side of the screen). 2. Click on the blue button on the Alpha Particles gun (lower left side of the screen) to start firing Alpha particles towards the gold foil. 3. Click on the Traces button (In the "Alpha Particles" box on the right side). What do you notice about the paths of most of the Alpha particles? When the number of protons is set at 20 and the Alpha Particle gun is firing Alpha particles towards the gold foil, most of the Alpha particles are shown to pass straight through the atom (atomic scale view). When duplicating the same scenario in the nuclear scale view, the traces from the Alpha particles are mostly passing straight except for the particles in close proximity of the nucleus which are scattering away from the nucleus and also pushing the other particles in their path away from the nucleus. (Positive charges repels other positive charges) 4. Increase the number of protons to 60. Does it change how the Alpha particles move? If so, how? When the number of protons is increased to 60, some Alpha particles still have a straight path, as seen in the atomic scale; however, it appears that more particles are deflecting away from the nucleus, scattering in various directions (small angular deflection). This is more evident when viewed in the nuclear scale view as the particles show hardly any movement in a straight path. 5. Now, increase the number of protons to 100. How does this increase change how the Alpha particles move through the gold foil as compared to when you started? Why do you think this change occurred? When the number of protons is increased to 100, most of the particles are deflecting away from the nucleus (atomic view). Again, this is more evident when viewed in the nuclear scale view as the particles show a greater trajectory away from the nucleus. It appears the increase in the number of protons causes the Alpha particles to deflect at a much larger angle. Since Alpha particles have a positive charge, the particles are repelling away from each other and because there are more protons, there are more nuclei in the path of the particles. 6. Take a screenshot with the proton number set to 100 and include it below. See above. 7. Repeat the above steps but vary how many neutrons (change it to 40 as an example). Does this change how the Alpha particles travel? Why or why not? The Rutherford Scattering simulation was reset and neutrons were changed to 20 as shown below. In the atomic view, most of the Alpha particles appear to travel straight through the atom with a few particlpes scattering off the nucleus at a large angle. The nuclear view, however, shows a much wider deflection away from the nucleus. Increasing the neutrons would not change the Alpha particles’ path because the neutrons are neutral (no charge), so there would not be reason for much change, as opposed to adding protons which would increase the charge and, therefore deflect away from the nucleus. 8. How are the situations in #6 and #7 different? Why do you think this is? In situation #6 the protons were increased and in situation #7 the neutrons were increased. In situation #7 the Alpha particles appear to deflect when closer to the nucleus as opposed to the particles in situation #6 which deflect much sooner than the ones in situation #7. As mentioned, in the #7 response, the neutrons have no charge which would not contribute to the Alpha particles’ path. Part 2: Plum-Pudding Atom Before beginning this exercise, be sure you have read in the text about Rutherford's Gold Foil experiment. This will help in your understanding of what is happening in this simulation (section 2.2, page 48). 1. Switch the simulation to the Plum-Pudding Atom (center of the page ~ under the pause/play buttons). 2. Once the simulation opens, click on the trace button (in the box on the right titled "Alpha Particles"). 3. Click on the blue button on the Alpha Particle gun to turn on the Alpha particles. What type of path do the Alpha particles take? Take a screenshot and include below with your description. The Alpha particles in this simulation are taking a straight path, through the atom. 4. How is this different than the Rutherford simulation? In the Plum Pudding simulation, the atom does not show a nucleus, therefore, the Alpha particles are traveling straight through the atom. The positive charge of the protons in the nuclei is what causes the deflection of the Alpha particles. Conclusion 1. Why do you think that our model of the atom changed after Rutherford’s experiment? Prior to Rutherford’s experiment, J.J. Thomson’s plum-pudding model surmised that electrons were “like raisins in a pudding or seeds in a watermelon” (Brown, LeMay, et al., 2018. P. 49). When Rutherford conducted his experiment, he, and Marsden, proved that the atom was not like the plum-pudding model. During Rutherford’s ɑ-scattering experiment, he was able to reveal that some of the “ɑ particles scattered at large angles because their path takes them very close to an extremely small but highly charged nucleus” (Brown, LeMay, et al., 2018, p. 49). By revealing scattering, Rutherford’s model has changed the way we can see and study the atom. 2. Why were the Alpha particles deflected by the nucleus and not attracted to it? Alpha particles are deflected by the nucleus due to the highly positively charged protons in the nucleus. If Beta particles were fired in the model, there would be a different result as Beta particles are negatively charged therefore, would be attracted to the positively charged protons.