CHEMISTRY LAB
Electrons: Probability
WAVE MECHANICAL VIEW OF THE
HYDROGEN ATOM
MATERIALS
Circular target
tape
Pen or dull pencil
meterstick
It has been determined that one can only estimate the
probability of finding an electron at certain locations around a
nucleus at any given instant. While it is impossible to
duplicate the conditions inside an atom, in this experiment
you will study the probability of certain objects coming to rest
at given distances from a target. In this way, you will be
better able to understand the probability of finding an
electron.
PROCEDURE
1.
Tape your target to the floor.
2.
Determine how high above the floor one meter is.
3.
Drop the pen or dull pencil from a height of one
meter onto the target. Aim for the center of the
target. Check to be sure your writing utensil left a
mark. If the target is missed entirely, repeat the trial.
4.
Repeat for a total of 100 trials (marks).
5.
Record the number of marks in each space on the
target in the data table provided. To be consistent,
record the lower of the two space numbers when a
mark lands on a line. Add up your marks to make
sure 100 trials were completed.
6.
Write your data on the board/overhead. When the
entire class has done this, copy the class data onto
your table.
7.
Construct a histogram (bar graph) of your group
data, with Area Number on the x-axis and Number
of Marks on the y-axis. Make sure your graph is
neat and has all the required labels and titles
provided. You will be graded on neatness.
READ
ALL
INSTRUCTIONS
BEFORE
PROCEEDING
SAFETY NOTE
8.
Construct a bar graph of the class averages, with the
same axes, labels, and spacing as the group data
bar graph. Again, make sure you understand that
neatness and labeling are important.
9.
Compare the two graphs from steps 7 and 8.
Explain any differences that may have occurred.
10.
Before you dropped the pen or pencil, could you
have predicted exactly where it would strike the
target?
11.
From your group graph, what is the most probable
distance from the center of the circle for the pencil to
make a mark? What about the class graph?
12.
If you could not predict the exact spot where the pen
would hit the target, could you predict the area within
which it would hit? Where would that be?
13.
One pen or pencil made all of the dots on the target.
How many electrons can make all of the “dots” that
form the electron cloud we call an orbital?
14.
How does the shape of your graphs compare to the
shape of the graph shown in class?
15.
What kind of orbital has an electron probability that is
the same as that used in this activity?
16.
If you were dropping small steel washers at a similar
target with a magnet at the center, what difference
would you expect to find when you plotted a graph of
the results? In what way would this be somewhat
like an atom with its nucleus and surrounding
electrons? How would it differ?
You may not perform unauthorized experiments such as evaluating
your accuracy when throwing pencils at objects or people. Such
unauthorized experiments will result in a zero for this laboratory
grade and the great displeasure of your instructor. You also may
not use markers or writing utensils that belong to your instructor
without his or her express permission.