POGIL Activity:
Alpha and Beta Decay Sims

Alpha Decay simulator

Use a computer to go to the following link: https://phet.colorado.edu/en/simulations/alpha-decay. Or try a search for “PhET Alpha Decay”. Load the simulator and then answer the following questions.

1. On the Multiple Atoms tab drag a single nucleus out of the bucket into the white area. Describe what happens. Use the Reset All Nuclei button to watch it again.
2. What is an alpha-particle? Define it by explaining what particles it is made of and give its atomic symbol.
3. Why is the nucleus a different element after the alpha-particle is emitted?
4. Why is the final isotope ²⁰⁷Pb and not ²⁰⁶Pb or ²⁰⁷Bi?
5. If a ⁴⁰K nucleus were to undergo alpha decay what would the nucleus turn into?
6. Determine the average amount of time it takes for one ²¹¹Po atom to decay by using the Single Atom tab. Simply observe the nucleus until it decays and then write down the time in the box at the top of the screen. Reset the nucleus until you have recorded a total of 12 times. Put your results in a small table below:
7. The half-life of ²¹¹Po is about 0.5 s. How many of the Decay Times you recorded are less than 0.5 s and how many are more than 0.5 s?
8. Are about half of your Decay Times less and half more than 0.5 s? If not, perhaps more data will help. Collect up to a total of 20 Decay Times and then answer this question again.
9. Is the Decay Time always about 0.5 s? Or is it random? Justify your answer.
10. Go back to the Multiple Atoms tab. Hit the Pause button at the bottom of the screen. Add 100 nuclei to the white area. You can count them using the display in the upper-left. Unpause the display. Do they all decay at once? Describe what happens.
11. By pausing and resetting the nuclei a few times see if you can determine how long it takes to get down to 50 left un-decayed. How long does it take to get down to a 50/50 mixture where 1/2 of the original number remains?
12. How long does it take to get down to a 25/75 mixture? (Where 25 nuclei are left un-decayed or 1/4 of the original number).
13. Change to the "Custom" isotope from polonium-211. Look at the top of the simulator and notice that the half-life is now adjustable. Pause the simulator using the button at the bottom. Set the half-life to something less than a half-second. Pull all of the atoms out of the bucket. Start the simulator. Pause, reset all nuclei, and set the half-life to the largest value possible. Start the simulator. Describe the difference in behavior between a type of atom with a short half-life and one with a long half-life.
14. What is the meaning of half-life?
15. If you had a piece of polonium in a drawer would it stay radioactive forever? Why or why not?
16. Which has more decay events per second, 10 or 100 nuclei? Use the sim to find out.
17. How does the rate at which atoms decay depend on the number of atoms?

Beta Decay simulator

Use a computer to go to the following link: https://phet.colorado.edu/en/simulations/beta-decay. Or try a search for “PhET Beta Decay”. Load the simulator and then answer the following questions.

18. On the Multiple Atoms tab drag a single atom out of the bucket into the white area. Describe what happens. Use the Reset All Nuclei button to watch it again.

You may have noticed that two particles are emitted by the nucleus in this simulator. The second particle is called a neutrino. The neutrino carries some of the energy and momentum of the decay away but interacts so poorly with other types of matter that billions of them pass through us every second and we never notice. It is a real thing but as it makes no difference in figuring out the results of beta decay for the nucleus we will ignore it.

19. What is a beta-particle? Define it by explaining what it is and give its atomic symbol.
20. Why is the nucleus a different element after the beta-particle is emitted? Look carefully at the protons and neutrons shown on the screen in the simulator.
21. Why is the final isotope ³He and not ²H or ⁴He?
22. If a ²⁸Al nucleus were to undergo beta decay what would the it turn into?
23. Use the simulator to estimate the half-life of hydrogen-3 (also called tritium).

24. On a separate piece of paper create an outline that contains all of the main points that you believe you were meant to learn by doing this activity. Do it with bullets or with headings and sub-headings (A., B., 1., 2., etc.) Work with your group on this part and consult with your teacher before moving on to the next part of the activity.
25. On a separate piece of paper use your outline to write a short paragraph that summarizes all of the main points you wrote above. Do this part completely independently but share your work with your group members after you are finished. Make any changes or additions you find necessary to make a final draft of this information. Type up this draft to turn in as the recorder’s report.