Beanium Lab
Name ______________________
Date __________Period _______
Introduction & Purpose:
What is an isotope? What does it mean to say that the atoms in a sample of an element are isotopes of
each other? Ordinary beans are a lot bigger than atoms, but perhaps they can give you one or two clues
about isotopes.
We have talked in class about isotopes: atoms of the same element that differ in mass. For example,
there are actually three different kinds of hydrogen atoms. Refer to the table below for the different kinds
(or isotopes) of two common atoms.
ISOTOPE
Protium
Deuterium
Tritium
Carbon-12
Carbon-14
PROTONS
1
1
1
6
6
ELECTRONS
1
1
1
6
6
NEUTRONS
0
1
2
6
8
SIGNIFICANCE
“normal” hydrogen
“heavy hydrogen”
radioactive hydrogen
“normal” carbon
carbon-14 dating
This lab exercise is designed to show you isotopes of an element in a simulation form, and how there
average masses are calculated. You will be asked to gather data about the “isotopes” and organize the
data. If atoms were as large as beans they could be sorted, counted, and massed. In this experiment we
will sort, count, and mass 2 different kinds of beans and imagine that we are observing 2 different
isotopes of the same element (let’s call it BEANIUM). The 2 different isotopes are greenium, and whitium.
Finally we will calculate the isotopic mass, in two ways and observe which calculation yields a more
accurate average mass.
Procedure:
1. Obtain a plastic cup which contains many atoms (beans) of BEANIUM.
2. Sort the atoms (beans) into a group for each isotope: white and green.
3. Record the total number of atoms:
a) Total number of atoms =
4. Record the percentage of the total that each isotope (color of bean) occurs
EXAMPLE: I counted 100 beans 98 of them are white and 2 of them are green. To find the
percentage for each I divide how many of each I have by the total amount of beans that exist.
White = 98/100 = 98%
Green = 2/100 = 2%
a) % occurrence of White =
b) % Occurrence of green =
5. Record the number of each type of isotope:
a) White =
b) Green =
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6. Record the mass of each type of isotope:
a) Mass of all the white beans =
b) Mass of all the green beans=
7. Determine the average mass of each isotope of beanium (this represents the isotopic mass)
EXAMPLE: I counted 340 white beans They have a mass of 80 grams. The average mass of
one white bean is 80 / 340 = 0.235 grams.
a) Average mass of one white bean =
b) Average mass of one green bean =
Calculating Averages
Straight Average:
To calculate the straight average mass of the beans perform the following equation:
Average mass of Green isotope + Average mass of White isotope
Number of isotopes
Straight Average Mass of Beanium=
Weighted Average:
To Calculate the weighted average for the beans you add up the (average masses of each color x each
beans % occurrence:
(% occurrence of white) x (Avg. mass of white)
(% occurrence of green) x (Avg. mass of green)
+
=
Weighted Average Mass of Beanium=
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Conclusion Focus Questions
1. What is the difference between the weighted and straight averages for the beans?
2. Which average mass was more accurate the straight average or weighted average?
3. What made that average more accurate?
4. How are the average masses on the periodic table calculated?
5. Why are the average masses calculated in this way?
6. Why are the mass numbers on the periodic table decimals and not whole numbers?
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