Name: ___________________________________________________
Period: ___
Thomson and Rutherford Simulation
J.J. Thomson and Ernest Rutherford are two major names in the history of atomic discovery. In this
simulation we will be seeing how Rutherford’s model was demonstrated to be more accurate than that
of Thomson.
Instructions:
1) Go to the URL: https://phet.colorado.edu/en/simulation/rutherford-scattering (alternatively,
search “PhET Rutherford Scattering”)
2) If it asks to update Java: Later
3) If it asks whether to run the program: Yes
4) First access the “Plum Pudding Atom” tab.
Plum Pudding Questions:
1) In this model, where is the positive charge?
2) In this model, where is the negative charge?
3) Looking at the Legend in the upper right corner, what is an alpha particle made of?
4) Start the simulation by clicking on the “gun” on the left side of the simulation. What happens to
the alpha particles?
5) How does moving the energy bar on the right of the simulation affect the alpha particles?
Rutherford Atom Questions:
6) Click on the “Rutherford Atom” tab of the simulation. In this model, where is the positive
charge?
7) In this model, where is the negative charge?
8) Start the simulation. What happens to the alpha particles?
9) Click on the check box labeled “Show traces.” Pause the simulation after a few seconds and do
a quick sketch of the paths of the alpha particles.
10) How are the paths of the alpha particles different in the Rutherford atom versus the Thomson
(Plum Pudding) atom?
11) Under the “Atom Properties” section, increase the number of protons to 100. What happens to
the alpha particle traces?
12) Now decrease the number of protons to 20. What happens to the alpha particle traces?
13) Set the protons back to 79. Run the simulation with neutrons at 20 and neutrons at 100. How
do these two compare with their alpha particle traces?
14) Given what you know about the structure of atoms, what do you think happened in Rutherford’s
gold foil experiment? (In other words, what happened to his alpha particles?)