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Beanium Isotopes (11 Favorites)

ACTIVITY in Isotopes, Measurements, Atomic Mass. Last updated October 14, 2019.


In this activity, students will determine the average atomic mass of a sample of an imaginary element called Beanium.

Grade Level

High School


By the end of this lesson, students should be able to

  • Determine the atomic mass from a mixture of isotopes

Chemistry Topics

This lesson supports students’ understanding of

  • Isotopes
  • Atomic mass


Teacher Preparation: 10 minutes

Lesson: 30 minutes


For each group:

  • 7 different types of beans
  • 100-mL beaker


No special safety considerations are required for this activity.

Teacher Notes

  • It may be helpful to work through a sample problem before having the students complete the activity.
  • Before the activity, mix together seven different types of bean in a large bowl. Include large amounts of three types of beans, with the other four in smaller quantities. These will be the “impurities”.
  • After the activity, point out to the students that the average atomic mass determined by each group should be very similar, even if their sample sizes were slightly different.

For the Student


The only research chemist at Anywhere High School has discovered a new element! This element was discovered in the mixture that makes up the baked beans in the cafeteria. The researchers have named this element Beanium. No tests have been done on this element because the researchers could not determine the atomic mass of this new ground breaking element.

There is a large sample of this new element in the lab at the research facility at the high school. A reporter has learned that this top secret facility is funded from the same people that fund AREA 51. As you may know, this secret funding comes from the international alien cover-up conspiracy started in Roswell, New Mexico in 1947.

This lowly research chemist has brought this new element to your classroom so that the lab technicians can determine the atomic mass of Beanium.


  • 100-mL beaker
  • Sample of Beanium


The different isotopes of Beanium are shaped like different types of beans.

  1. Sort the Beanium sample into the different isotopes. Record the number of each isotope in the data table provided.
  2. Find the mass of each isotope. This is not the mass of one atom, it is the mass of all the atoms of that particular isotope. Record these masses in the data table.
  3. Follow the directions in the data table, and use your vast knowledge of average atomic masses to find the atomic mass of Beanium.


Beanium Data Table: Use only the three isotopes with the greatest number of atoms are to be recorded. (Any others are impurities)

Isotope #1 Isotope #2 Isotope #3
# of atoms

Total number of atoms in your sample________________

(add up the # of atoms of all 3 isotopes)

(# atoms / total atoms)
(rounded to nearest .01)

Mass of Sample

Mass of one atom
(mass of sample/ # of atoms)
(rounded to nearest .01)


To find the atomic mass of Beanium, use the mass of one atom of each isotope as the mass number and the percent of each isotope.

Show your work below:

The atomic mass of Beanium is __________________amu