Download AVERAGE ATOMIC MASS LAB

Beanium
Name _______________________________________________
Date __________
NEWS FLASH!!! A NEW ELEMENT HAS BEEN DISCOVERED.
Springfield USA—Nuclear Chemists, performing basic research on food
products at Springfield Power Plant, have discovered what is believed to be a
new element. Mr. Burns, the plant’s owner, says, “We have tentatively
named this element Beanium.” Mr. Smithers, assistant to Mr. Burns adds,
“We derived this element from the protein nodules we put into our chili.”
Further research of the new element will be conducted in more suitable
surroundings, namely laboratories in a nearby school. Because Springfield
apparently only has an elementary school, research work has been
contracted to neighboring Arlington High School. Many chemistry students
have generously volunteered their time and expertise to help with the followup experiments involving the new element.
Dr. Julius Hibbert says the first follow-up experiments conducted at Arlington High School will
determine how many isotopes of this element exist. The second experiment will determine the mass
of each isotope. The third experiment will determine the percent abundance of each isotope. The
final calculations will discover the average atomic mass of the new element.
“One unique property of Beanium should make these experiments particularly easy—unlike
normal atoms, Beanium atoms are very large.” says Mr. Smithers. “They can be easily seen, and
different isotopes can be sorted by hand.”
Scientists are expecting a complete, comprehensive summary of this new element within two
days.
“This is the most exciting Chemistry discovery this century!” exclaimed Mr. Burns.
Purpose: To fully characterize the average atomic mass of the new element, “Beanium”.
Materials: Balance, Sample of Beanium, Calculator
Procedure:
1. Sort your Beanium sample into the different isotopes (by color.)
2. Count the number of atoms for each isotope present in your bag and record the results in the
data table below.
3. Find the total mass of each isotope in your bag and record the results in the data table.
4. Calculate the average atomic mass of one atom of each isotope by dividing the total mass by
the number of atoms in that isotope. Show your work in the space below and write your results
in the data table.
5. Calculate the percent abundance of each of the isotopes by dividing the total isotopic mass for
each color by the total mass of all of the atoms, then multiplying by 100. Show your work in
the space below and write your results in the data table.
6. Calculate the weighted average atomic mass of Beanium to be placed on the Periodic Table
by multiplying each average atomic mass by its percent abundance, adding them all together,
and then dividing by 100. Show all work and circle your answer.
Data:
Isotope Color
Total
Number of Atoms
Total Isotopic
Mass
Average Atomic
Mass
--
Percent
Abundance
Conclusion Questions:
1. What are the atomic differences and similarities between isotopes of an element?
2. Find the non-weighted average mass of Beanium by dividing the total mass of all of the
isotopes by the total number of atoms. Compare this number to the weighted average mass
calculated in #6 and explain any differences.
3. If the heaviest isotope was more abundant, and the other two isotopes were less abundant,
what would happen to the atomic weight of Beanium? Why?
4. A student obtained the following data about a sample of an unknown element:
Isotope
A
B
Total
# of Atoms
40
160
Mass of Sample (amu)
400
1760
a. Calculate the percent abundance of each isotope.
b. Calculate the average mass of one atom of each isotope.
c. Calculate the average atomic mass of the unknown element
d. Which element is this? __________________