Download Atomic Mass Lab (Flaskum)

Atomic Mass Lab (Flaskum)
Introduction:
The atomic mass of an atom is equal to the sum of the protons and neutrons in the atom’s nucleus. Since both the
proton and neutron have a mass of 1 amu, the mass of an atom is measured in atomic mass units. Because atoms are
so small, it is impossible to count the number of protons and neutrons in the nucleus of an actual atom. Models can
be used to develop the idea of atomic mass.
According to the contemporary atomic theory, all atoms of an element are not exactly alike. Each atom of an
element has the same number of protons but the number of neutrons may differ. Atoms with the same number of
protons but different numbers of neutrons are called isotopes. When the masses of all isotopes of an element are
known, the average atomic mass of the element can be calculated.
Purpose:
1. To use a model of an atom to find the atom’s atomic mass.
2. To distinguish between atoms of the same element and those of a different element.
3. To calculate the average atomic mass of an imaginary element.
Materials:
Erlenmeyer flasks, red thumb tacks, green thumb tacks
Procedure:
1. The imaginary planet, Erlenmeyer, consists of only a few elements, the most common of which is known
as Flaskum (symbol = Fk). All elements from the planet Erlenmeyer have protons which are red thumb
tacks and neutrons which are green thumbtacks. The classroom contains a representative sample of the
planet Erlenmeyer.
2. Carefully examine each atom present in the room.
3. Count and record the number of protons and neutrons each atom contains.
Data: Record your data in the table below.
Atom
Number
Atomic
Number
Number of Protons
Number of
Neutrons
Atomic Mass
Number
Calculations and Questions
1. How many atoms of Flaskum does the sample contain?
2. How many other elements are present?
3. How can you distinguish one element from another?
4. How many isotopes of Flaskum are present?
5. Calculate the average atomic mass of Flaskum using the mass number and percent abundance. (Show all
calculations and label all values)
6. Were any of the atoms observed to have a fraction of a proton or a neutron? Is there an isotope of Flaskum that
exists with the average atomic mass? Why or why not?
7. Which isotope of Flaskum is the most common? How could you estimate this from the average atomic mass, if
you had not done an actual survey, as in this lab?
8. Neon exists as two isotopes: 90.000% neon-20, and 10.000% neon-22. Using the mass number, calculate the
average atomic mass.
9. Use the following information to calculate the average atomic mass from the relative masses.
Abundance
Species
Relative Atomic Mass (amu)
69.17%
copper-63
62.939 598
30.83%
copper-65
64.927 793
10. The atomic mass of chlorine on the periodic table is not a whole number. What does this indicate? What is the
most common isotope of chlorine?