Average Atomic Mass of Beanium

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					Chap 3 Lab: Atomic Mass of Beanium                        Name: ___________________________________

Introduction: Write a paragraph defining what an isotope is and what effect the number of neutrons has on
the atom. Include a discussion of what “percent abundance” means.

Purpose: To analyze the isotopes of beanium and to calculate its atomic mass.

   1) Obtain a sample of beanium isotopes by scooping up a beaker full of beans from the bean container.
   2) Separate the beans by isotope and count them. Record in “# of beans” section of data table.
   3) For each isotope sample of beanium, determine its total mass using the balance. Record in table.
   4) For each isotope, calculate the average mass of one bean by dividing the total mass of that isotope by
      the number of beans of that isotope. Record in table.
   5) For each isotope, calculate its percent abundance by dividing the number of beans in each isotope by
      the total number of beans.
   6) Calculate the average atomic mass of beanium by first multiplying each isotope’s average mass by its
      percent abundance and then adding these values together.


                # of beans      Total mass of beans          Average mass of             % Abundance of
                 (atoms)              (grams)                 1 bean (grams)            each type of bean




Small Brown


Total number of bean element atoms in cup = _________

Calculations: (you must show work)
      Determine the average atomic mass of beanium.

            Remember the equation for average atomic mass:

            Atomic Mass = (% abundance A)(mass A) + (% abundance B)(mass B) + ….

Conclusions: (write in complete sentences)

1) Why is it important to calculate a weighted average for atomic mass and not just a normal average?

2) Explain the differences between the atomic mass of your beanium sample and that of your neighbor group.
      Explain why the difference would be smaller if larger samples were used.