“Beadium” Lab—Beads as Isotopes
Name: __________________________________________ Period: _________
Introduction: In this lab, you will pretend that two different colors of beads represent the
isotopes of the element “beadium”. The green beads are the heavy isotope and the pink beads
are the lighter isotope. The task will be to determine the percentage of each isotope in a mixture
of isotopes without counting them.
Materials: pink and green beads
1. Obtain exactly 10 green beads. Weigh them and record the mass. Calculate the mass of
a single green bead.
2. Obtain exactly 10 pink beads. Weigh them and record the mass. Calculate the average
mass of a single pink bead.
3. Prepare a mixture of exactly 100 beads to give to another group. You may make any
combination you like (ex: 66 green and 34 pink). Do NOT tell them how many of each
color! Another group will make a mixture for you.
4. When you receive a mixture from another group, weigh the entire mixture. Do NOT sort
them by color or count them! Calculate the average mass of a single bead in the mixture.
5. Using the equation for average atomic mass, calculate the number of each color of bead
in the mixture that the other group gives you. Afterwards, check with the group that gave
you the beads or just count them yourselves.
Required Participation: Behave appropriately in lab, conduct the experiments as
instructed, and clean up. You must fill out the data table and get my initials.
This lab write-up is a menu option worth 20 points—you must get initials, fill out the data table,
do the calculations, and answer the post-lab questions.
My initials (1 pt): ___________
Data Table (4 pts)—Required!
Your own beads Beads you receive
from another group
Quantity Green Pink Mixture
Number of beads 10 10 100
Average mass of a
Calculations (8 pts)—you MUST show work!
1. Calculate the fraction of green beads (X) in the mixture using the following:
Mmix = Mgreen (X) + Mpink (1-X) where
Mmix = the average mass of a single bead in the mixture
Mgreen = the average mass of a single green bead
Mpink = the average mass of a single pink bead
X = the fraction of green beads in the mixture
1-X = the fraction of pink beads in the mixture
2. What is the percentage of green beads in the mixture?
3. What is the percentage of pink beads in the mixture?
Post-Lab Questions (7 pts)
You may use your notes and packet to help answer these questions, but you MUST work by
yourself! Do not copy anyone else’s words and don’t let anyone copy yours!
Answer in complete sentences!
1. How are the two isotopes (green and pink) of beadium alike?
How are they different?
2. Look at the data table; is the average mass of a bead in the mixture closer to the mass of a
pink bead or closer to the mass of a green bead?
Explain what that indicates about the relative number of pink and green beads in the
3. You had exactly 100 beads in your mixture. Therefore, if you had 54% green that would
mean you had 54 green beads. Did you get a whole number for a percent? Did you get
the right answer? If no for either question, give at least one reason why not.
Use the periodic table for questions 4 & 5:
4. The element copper is made up of two isotopes: copper-63 and copper-65.
a. Copper-63 has: how many protons? _______ neutrons? ________
b. Copper-65 has: how many protons? _______ neutrons? ________
5. Get the average atomic mass of copper from the periodic table: ___________________
Why is the average not 64? What does the average indicate about the amount of copper-63