Name(s): __________________________________
Pd. ___________
BAG O’ ISOTOPES
Introduction:
Scientists have recently discovered the element legumium. Your assignment is to
calculate the average atomic mass of legumium based on the samples provided. The
atomic number of legumium is 4. The smallest of the isotopes, legumium-4, has an
atomic mass of 4 atomic mass units (amu). Legumium-5, the intermediate isotope, has
an atomic mass of 5 amu. The largest isotope, legumium-6, has an atomic mass of 6
amu.
Terms: Define the following terms before beginning the exercise.
Isotope
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Mass number
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Atomic mass
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Average atomic mass
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Purpose:
To calculate the average atomic mass of the newly discovered element, legumium.
Procedure:
1. Count and record in the table below the total number of isotopes in the sample.
2. Count and record in the table below the number of each legumium isotope.
3. Record the masses (provided in the introduction) of each legumium isotope in the
table below.
4. Calculate the average atomic mass of legumium using the following equation.
Average Atomic Mass = (% abundance Isotope 1 x Mass Isotope 1)+ (% abundance
Isotope 2 x Mass Isotope 2)+(% abundance Isotope 3 x Mass Isotope 3)
Name(s): __________________________________
Pd. ___________
Data and Calculations:
Total Number of Legumium Isotopes in Sample:______________
Isotope
Legumium-4
Legumium-5
Legumium-6
Quantity
% Abundance
Mass (amu)
Show calculation for Average Atomic Mass of Legumium:
Average Atomic Mass of Legumium:_______________
Discussion Questions:
1. Calculate the number of neutrons in each legumium isotope.
2. According to the sample, which legumium isotope is most abundant in nature?
3. If additional legumium-5 isotopes were added to the sample, how would the average
atomic mass of legumium be affected?
Name(s): __________________________________
Pd. ___________
Part 2:
In this part of the lab, you find the percent abundance of pennium and calculate the
average atomic mass for a sample of pennium.
Pennium
Find one of the containers containing atoms of pennium. Container letter: _________
Using a balance, find the mass of each of the pennies in the container. Record the year
and the mass of each penny in the table below. You might not use all of the spaces.
Year
Mass (g)
Year
Mass (g)
Year
Mass (g)
Summary of Data:
We will consider all of the pennies minted before 1982 as one isotope of pennium and all the pennies
minted after 1982 as another isotope of pennium, why?
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What is different about isotopes of atoms? How is this similar to what we see in the pennies?
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Name(s): __________________________________
Pd. ___________
Calculate the % Abundance of each isotope below. Show work below.
Isotope 1
Isotope 2
Calculate the Average Mass for Each Isotope of Pennium by adding up all of the
masses of that particular isotope and dividing by the number of atoms of that isotope
(show some work or give a brief explanation)
ISOTOPE 1
ISOTOPE 2
Calculate the Overall Average Atomic Mass of Pennium by using the Average Atomic
Mass of each isotope (calculated in the previous step, above) and the % abundance of
each isotope (show work).
Questions:
1. What do the pennies represent in this investigation?
2. What do the different masses of the pennies represent?
3. What information do you need to calculate the average atomic mass of an element?
4. How can you explain that there are different “isotopes” of pennium?