ELECTRON PROBABILITY DISTRIBUTION SIMULAITON
56 points
PURPOSE: (1 point, copy down off board)
INTRODUCTION: As it is impossible to see an electron in an atom, it is even more impossible to
describe its location by using exact coordinates. Scientists have ventured to calculate probable electron
densities through the use of quantum mechanics, which use rather sophisticated equations way beyond
our comprehension. This lab will simulate the location (most probable) of an electron as it rotates
around the atom.
In this experiment we will define regions around a particle point with a set of concentric circles.
The point represents the nucleus and the rings, regions of electron possibilities. The probe you drop will
represent the electron in these regions. The center of the target represents the nucleus. We will be
looking at the region where we would expect to find the electron 95% of the time.
At the conclusion of this experiment, you will determine the radius of maximum probability by
plotting a graph of your data.
MATERIALS: paper target, tape, very sharp pencil, marker
PROCEDURE:
1. Tape the target to a piece of cardboard
2. Standing with your arm outstretched, drop the very sharp pencil over the target. If it doesn’t
hit the target, rearrange your alignment.
3. Drop the pencil 100 times, making the location when it falls with a dot from the marker.
Make the dots very small because they are going to accumulate.
4. Locate the 95 dots that are closest to the center. Draw a smooth line around these points (it
doesn’t have to be a circle).
5. Count the number of dots in each concentric circle and record the data in the table.
6. Divide the number of dots by the area of the given region. This quotient is dots/cm2.
7. Multiply the last value by 10 to give a number that is more easily plotted.
8. Prepare a graph by plotting the (dots per cm2  101) on the y-axis and the (average radial
distance, cm) on the x-axis. (10 points)
DATA TABLE (10 points)
Number of
Average Radial
Circular Area
Distance of Area
Increment
Increment from
Bullseye
1
R1 = 0.50 cm
Area of
Increment
.79 cm2
2
R2 = 2.00 cm
12.57 cm2
3
R3 = 4.00 cm
50.27 cm2
4
R4 = 6.00 cm
113.10 cm2
5
R5 = 8.00 cm
201.06 cm2
Number of Dots in
Area Increment
Dots per Unit Area
Times 10
QUESTIONS: (5 point each)
1. What is your radius of maximum probability?
2. How does your graph compare to the other lab groups?
3. Should they all be the same? Why or why not?
4. Define probability:
5. What is the shape of your electron cloud? What is the accepted shape of the electron cloud for
an “s” electron? Look in your book or the web.
6. Define/describe the quantum model of the atom.
7. How is the quantum mechanical model of the atom different from Bohr’s model?