General Chemistry
Rutherford Simulation Lab
Name:_________________________
Date:_________________Hour:_______
*Learning Targets Met: Explain how the idea of the atom has changed over time.
Describe the atom as having a positive nucleus and negative electrons.
COMMON LAB ACTIVITY 3: Simulate Rutherford Experiment
Introduction/Background
Ernest Rutherford received the Nobel Prize in Chemistry in 1908 for his investigations into the
disintegration of the elements as a result of radioactive decay. Among the products of radioactive decay of
elements are alpha particles—small, positively charged particles. In learning more, Rutherford and his coworkers began studying what happened when a narrow beam of alpha particles was directed at a thin piece of
gold foil. The team measured the angles at which the particles were deflected from their former straight-line
paths as they emerged from the foil. This is shown in Figure 1 below.
As expected, Rutherford and his team found that most of the particles passed right through the thin foil
and were detected on the other side. What was unexpected, however, was a very few of the particles were
actually reflected right back toward the source or deflected to the side, having been “scattered” or bent due to
their encounters with the metal atoms in the foil target. This can be seen in Figure 1.
Rutherford went on to reason that only a very concentrated positive charge, located somewhere within
a gold atom, could possibly repel fast-moving, positively charged alpha particles sufficiently to reverse their
direction of travel.
Rutherford’s scattering experiments have been described as a “black box” experiment. The properties
of the positively charged particles were at least partially understood. The atoms making up the target (the foil)
presented Rutherford with a sort of black box—the structure of the atom was not known at the time. In order
to explain the results of the experiment, Rutherford had to unlock the “black box,” that is, he had to solve the
structure of the atom. This is what he proposed in 1911 as the model for the structure of the atom:
 Most of the mass of the atom is concentrated in a very small, dense area, later called the
nucleus.
 The rest of the atom is apparently “empty space.” (Most of the particles went straight through
the foil as if nothing was in their path).
 The central, dense core of the atom is positively charged. (As the particles randomly struck the
gold foil, a few approached the nucleus head-on and these were strongly repelled by the positive
charge, causing them to bounce back or recoil).
It is not practical to recreate Rutherford’s original scattering experiments. However, a simulation of the
concept can be done using marbles.
FIGURE 1
General Chemistry
Rutherford Simulation Lab
Name:_________________________
Date:_________________Hour:_______
General Chemistry
Name:_________________________
Rutherford Simulation Lab
Date:_________________Hour:_______
Materials
Marbles
meter stick
masking tape
Procedure
1.
Make a masking tape line, 60 cm long, on the floor. Use the meter stick to mark
the tape at 5, 15, 25, 35, 45, and 55 cm. Also, use a small piece of tape to mark a
spot about 1 meter away from the center of the tape.
2.
Place six of the marbles along the long piece of tape, one at each of the marked
spots. Place one marble on the small piece of tape.
3.
With eyes closed, one team member will roll the single marble toward the line of
marbles. The second team member will note whether this marble hits any of the
other marbles or misses.
4.
All of the marbles are returned to their original positions and the process is
repeated for a total of 75 tallied trials.
Data Table
Your Trials
Class Data
Marble HITS
Marble MISSES
TOTAL ROLLS
75
Post-Lab/Analysis Questions—Refer to the lab, introduction and diagrams to answer the following questions.
1.
Calculate the diameter of ONE MARBLE (in cm) with YOUR set of data. Show work.
HINT: Use the data with the following formula.
(𝐹𝑖𝑒𝑙𝑑 𝑊𝑖𝑑𝑡ℎ)(𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝐻𝑖𝑡𝑠)
= __________𝑐𝑚
(2)(#𝑇𝑎𝑟𝑔𝑒𝑡 𝑀𝑎𝑟𝑏𝑙𝑒𝑠)(#𝑇𝑜𝑡𝑎𝑙 𝑅𝑜𝑙𝑙𝑠)
2.
Calculate the diameter of ONE MARBLE (in cm) with the CLASS DATA set of data. Show work.
HINT: Use the data with the following formula.
(𝐹𝑖𝑒𝑙𝑑 𝑊𝑖𝑑𝑡ℎ)(𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝐻𝑖𝑡𝑠)
= __________𝑐𝑚
(2)(#𝑇𝑎𝑟𝑔𝑒𝑡 𝑀𝑎𝑟𝑏𝑙𝑒𝑠)(#𝑇𝑜𝑡𝑎𝑙 𝑅𝑜𝑙𝑙𝑠)
3.
Calculate the percent error for YOUR data. Show work. The actual diameter of one marble is 1.67 cm.
Percent Error =
|𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 𝑑𝑖𝑎𝑚𝑒𝑟−𝐴𝑐𝑡𝑢𝑎𝑙 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟|
𝐴𝑐𝑡𝑢𝑎𝑙 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟
X 100
General Chemistry
Name:_________________________
Rutherford Simulation Lab
Date:_________________Hour:_______
4. Calculate the percent error for the CLASS DATA. Show work. The actual diameter of one marble is 1.67 cm.
Percent Error =
|𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 𝑑𝑖𝑎𝑚𝑒𝑟−𝐴𝑐𝑡𝑢𝑎𝑙 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟|
𝐴𝑐𝑡𝑢𝑎𝑙 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟
X 100
5.
Which data gave the best results? Explain why you think that data had better results.
6.
Compare this activity to Rutherford’s Gold Foil Experiment. In what ways do you think this activity simulated Rutherford’s
efforts to determine the structure of the atom? In what ways was it different? Be specific—consider the size, speed and charge
of both the particles and the target. HINT: The width of the area represented the atom; the marble you rolled represented the
alpha ray particles and the marbles aimed at represented the protons or nuclei in the atom(s).
ANSWER QUESTIONS #7-14 BASED ON RUTHERFORD’S EXPERIMENT SPECIFICALLY, NOT ON THIS LAB ACTIVITY.
7.
What kinds of particles are being emitted by the radioactive source? What is their charge?
8.
Towards what are the alpha particles being directed?
9.
What happens when the charged particles strike the surface of the gold foil?
10. What was the purpose of the fluorescent deflecting screen?
11. What did Rutherord conclude from this gold foil experiment regarding the amount of empty space in the atom? Why was he able to conclude
this?
12. How does the deflection path of a charged particle that strikes the center of a gold atom differ from the path of a particle that only passes
near the center?
13. Based on this experiment, what did Rutherford conclude about the nucleus of the atom? Why was he able to conclude this?
14. ***What would have been observed if the positive charge of an atom (the protons) had been thinly spread out throughout the atom (instead
of the electrons being spread out)?