Name
Date
Exploring nuclear decay – Alpha Decay
Go to PhET Simulations. Find and open the sim called Alpha Decay.
http://phet.colorado.edu/simulations/sims.php?sim=Alpha_Decay
 Click on ‘Run Now’ to start the simulation. When the simulation
opens click on the ‘Single Atom’ Tab.
After the simulation begins, follow the instructions below and
answer the questions that follow each instruction.
1. Click on ‘Run Now’ and Watch the Polonium-211 (211Po) nucleus
until it decays. Click on the ‘Reset Nucleus’ button and watch it
again. Repeat this at least 8 more times. List at least 3 observations that compare the 211Po
nucleus before and after it decays.
2. Click on the ‘Reset Nucleus’ button and run the program again, but this time click the
‘Pause’ button
immediately after the decay so you can look at the particle that flies out of
the nucleus. What is this particle made of?
3. Why does the mass number change from 211 to 207 after the polonium nucleus decays?
4. Why does the polonium (Po) become lead (Pb) after a decay? (You may have to look at a
Periodic Table to determine this.)
5. Look at the ‘Decay Time Chart’ across the top of the screen. It should display the decayed
nuclei of all of the trials you ran. Does there appear to be any pattern for the decay times that
are represented on the chart? What does this tell you about the decay of a specific nucleus
having a predictable pattern or being random?
6. Now click on ‘Multiple Atoms’ and quickly empty the Bucket o’ Polonium by rapidly
clicking the ‘Add 10’ button 4 to 6 times. Watch the nuclei decay and watch the Decay
Chart across the top. List 3 observations concerning the decay. Print out the screen if
possible or draw what the Decay Chart across the top looks like.
7. Click the pause button
and then click the “Reset All Nuclei” button. Be prepared to make
observations. Run the program. Is the pattern of decayed nuclei across the top the same as it
was the first time? Print out the screen or copy the Decay Chart on your paper. You might
have to repeat this a few times to be sure of your answer. Describe any similarities and/or
differences in what you see when you do this.
8. Use the timeline on the top of the simulator as
a timer. Click on ‘Reset All Nuclei’ again and
click the ‘Pause’ button every 5 years to take
your data. Make a data table in the space on
the right showing the time in 5 year
increments and the number of 211Po nuclei
left after each 5 year time period. What
should the first data point for everyone be?
Data Table
9. Make a graph of the data above plotting
time on the horizontal axis and the
number of Polonium-211 nuclei on the
vertical axis. Label your axes. You will
need to pick the best scale for both axes
so the data fits nicely on the graph.
Does the graph resemble any
mathematical function you know of, for
example a straight line (linear),
parabolic, exponential or other?
10. EXTRA CREDIT: Try out a Bucket o’ Custom Atoms. How does changing the half-life
affect the pattern of decayed nuclei in the Decay Chart? Give a detailed explanation of what
happens and give reasons for these observations.