Uploaded by Laura Schmidt

electron probability lab

Lab partner(s):
Schrodinger’s Electron Probability Lab Activity
Purpose: For this lab activity, you will use marbles, carbon paper, and a target to investigate the three-dimensional
distribution of the electron in the ground state orbital of hydrogen. While this is a two-dimensional model, we are using
it to help you better understand the way electrons in the ground state orbital of hydrogen can be three-dimensionally
Laird, Brian B. University Chemistry, pp. 98-106.
The position of an electron in an atom at a given moment cannot be predicted. The region of space in
which the electron can probably be found is called an orbital. Orbitals are often referred to as “electron
clouds” because they are not absolute. In fact, there are times when an electron may be found outside
the orbital.
The ground state orbital of hydrogen is represented by a fuzzy sphere with the nucleus at the center. The
denser areas of sphere represent areas where there is a greater probability of finding an electron. Since
the electron in a hydrogen atom is in constant motion, it may be helpful to compare the electron cloud to
spinning fan blades. Even though there is a finite number of blades, they appear to fill the complete
circle through which they turn. In the same manner, the single electron of a hydrogen atom appears to
fill the entire electron cloud.
Materials: marbles, carbon copy paper, target, meter stick
Place your target on the floor with a sheet of carbon paper taped to the top of the target, making sure the
carbon paper is facing towards the target. Make sure that the target is flat, and that the carbon paper is
smoothly placed over the top of the target.
Drop your marbles from a height of approximately 100 cm above the carbon paper so that the marble imprints a
mark from the carbon paper onto the target. Make sure that you aim for the center of the target, repeating this
50 times. Make sure that you do not throw the marbles down; just let them drop and fall freely from your hand,
aiming for the center of the target.
Next to the target, a second student should catch the marble after it hits the target, not letting it hit the target a
second time.
Once you have done your 50 drops, count the number of marks in each of the numbered regions of the target
and record these numbers in the data table. It is best to circle the marks with a pencil to avoid counting a
mark twice.
If a carbon mark from a marble is completely within an area, it belongs to that area.
If the carbon mark is on a line, it belongs to the area that the greater portion of its mark occupies.
If the mark is on a line, and it seems t be equally in two area, it belongs to the area nearest to the center.
Any part of a carbon mark counts as a complete mark.
Data Table 1:
|Region for 1st trials
Number of marks for 1st trials
Region for 2nd trials
Make sure that you have all of your dots circles.
Now, drop from a height of 150 cm. Only do this height drop 20 times.
Circle the 10 new dots with a different color, and record that data.
Count the number of marks per region as you did in steps #5-8 above.
Number of marks for 2nd trials
1. What region is an “electron” (carbon mark) most likely to be found in? ______
Least likely (besides 0)? _______
2. Before you dropped your marble, could you predict exactly where it would strike the target? ______
3. If you could not predict the exact spot where the marble would hit the target, could you predict the area within
which it would hit? ________
4. One marble made all of the dots on the target. How many electrons does our model simulate when making all of
the dots that form our “electron cloud” on the target? ____
5. Describe what happened differently when you dropped from the 150 cm instead of the 100 cm. What was different
about the overall results?
From middle school science, you know that an object has more potential energy if it is located higher up. If a
marble has more potential energy at the top, it should have more of what type of energy when it hits the ground?
If an electron drops from a higher up level, will it release more or less energy than one that drops from a lower
o The one that drops from a higher up level will release _______________________ than the one the drops
from a lower level.
8. Compare and contrast Bohr’s model of the atom with Schrödinger’s electron cloud model of the atom. (You should
describe similarities AND differences).