Name _____________________________________________________ Period ____________
Chapter 4: Atomic Structure
Keller/Rosenzweig
Average Atomic Mass of the Element Beanium
PURPOSE: To determine the average atomic mass of the element Beanium.
MATERIALS: Sample of element Beanium, balance, weighing dish
PROCEDURE:
1. Obtain a sample of element Beanium. The sample contains atoms of three known
isotopes of the element Beanium – red beans, navy beans (white), and pinto beans
(speckled).
2. Sort your Beanium sample by isotope (make 3 piles) and count the Number of atoms
present in for each isotope of Beanium (bean types). Record the number of atoms in the
data table below.
3. To find the TOTAL number of atoms, add up the total number of Beans and Record in
data table. Record this number in your data table.
4. Find the mass of each individual isotope using a balance. Turn on the balance and set it
to zero. Place the weighing dish on the balance and tare the balance (reset the balance to
zero with the weighing dish still on it). Add all the red beans to the weighing dish.
Record this as the “total mass of isotope” for the red beans in the data table below.
5. Repeat step 4 for the navy beans, then the pinto beans.
6. Determine the Average mass of one atom for the red bean by dividing the total mass of
the isotope by the number of atoms present. Record in data table. Repeat for navy beans
and pinto beans.
7. Calculate the Percent abundance of red beans in the sample by dividing number of
atoms of red beans by the total number of atoms in the sample. Use the equation below.
# Red atoms
x 100
Total Beans in sample
DATA TABLE
Red
Navy
Pinto
Total
Number of atoms
Total mass of isotope
Average mass of one atom
Percent abundance of isotope
XXXXXX
XXXXXX
XXXXXX
XXXXXX
100 %
8. Calculate the average atomic mass of element Beanium. Use the average mass of one
atom when calculating with mass.
QUESTIONS:
The data table below contains information on three key isotopes of calcium:
1.
40
Ca, 44Ca, and 42Ca are all isotopes of the element calcium. How many protons,
neutrons, and electrons does each isotope contain?
Isotope
Protons
Neutrons
Electrons
40
Ca
44
Ca
42
Ca
2. Calculate the average atomic mass of calcium based on the given data.
Isotope
40
Ca
44
Ca
42
Ca
Atomic Mass (amu)
39.96
43.95
42.00
Natural Percent Abundance
96.9%
2.1%
1.0%
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3. Silver has two naturally occurring isotopes, 107
47𝐴𝑔 has a mass of 106.905amu (52.00%) and
109
47𝐴𝑔 has a mass of 108.905amu (48.00%). What is the average atomic mass of silver?
__________________
4. Data for chromium’s isotopes are given below. Calculate chromium’s average atomic mass.
Isotope
Cr-50
Cr-52
Cr-53
Cr-54
Chromium Isotope Data
Percent Abundance
4.35%
83.80%
9.50%
2.35%
Mass (amu)
49.95
51.94
52.94
53.94
__________________
5. Complete the chart below:
NAME
a.
SYMBOL
ATOMIC
NUMBER
ATOMIC
MASS
NUMBER
PROTONS
NEUTRONS
80
122
ELECTRONS
francium
b.
Ba
c.
25
58
d. strontium-90
e.
f.
15
18
Ni+2
g.
h. rubidium-88 ion
36
6. Write out the isotopic notation for each of the particles in #5. Be sure to include element
symbol, atomic number, mass number and charge (when necessary).
a.
b.
c.
d.
e.
f.
g.
h.