Graphing Ionization Energy
Curriculum Placement
Chapter 11, section 11.4 in World of Chemistry
Teaching Notes
This activity can be completed when discussing ionization energy in detail. It is a good way
to visually represent and analyze how the ionization energies of elements on the periodic
table are related to one another (and to explain why these trends do or do not occur). Before
doing this activity, the students should have a basic understanding of what graphing and
ionization energy means.
The activity should take approximately 60 minutes to complete although creating the graph
should only take about 20–30 minutes (and the discussion questions could be completed as
homework if needed). The activity can be done individually or in small groups.
Materials needed for the activity are graph paper, scotch tape, rulers, pencils, and periodic
tables or general tables that include the ionization energy of each element (through atomic
number 94).
Included is a blackline master to be copied and distributed to your students at the beginning
of the activity.
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World of Chemistry
Graphing Ionization Energy
Purpose
To understand what ionization energy means and how it relates to trends in the
periodic table.
Materials
graph paper (two sheets)
scotch tape
ruler
pencil
table with ionization energies of the elements
Procedure
1.
2.
3.
4.
Tape two pieces of graph paper together so that the horizontal or x-axis is as long
as possible (tape the short sides together).
On the x-axis, number consecutively from 1 to 94 and label this axis “Atomic
Number.” On the y-axis, number consecutively from 0 to 25 and label this axis
“First Ionization Energy.” The units will be in volts.
Plot the ionization energy for each element according to its atomic number.
Carefully circle each data point and connect the points consecutively with a solid
line. Where there are no values for a particular number, use dashed lines to
suggest where you think the line would go. Do this all in pencil.
Beside each point, neatly write the symbol for the element.
Analysis
1.
2.
3.
Make a list of the elements from the peaks on your graph. Are these related as a
group?
a. Now make a list of the low points on the graph. These come just after the
peaks. How can you explain this great drop in the first ionization energy?
b. Are these elements related on the periodic table?
a. Now study the graph between sodium and argon. Explain the pattern.
b. Why might magnesium be higher on the graph than aluminum?
c. Why might phosphorus be higher than sulfur?
d. Why does the same pattern exist from lithium to neon?
e. What about from potassium to krypton?
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44
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4.
5.
6.
7.
a. What new type(s) of elements do you notice in the pattern between potassium
and krypton?
b. What are the new elements?
c. How many of them are there?
d. Do you expect them to behave alike? Why or why not?
Now study the elements in the carbon group: C, Si, Ge, Sn, Pb. In general how
does the ionization energy change in going down the group? Explain why this
happens.
a. Can you locate the f groups of elements without looking at the atomic
numbers?
b. Study the graph from atomic number 37 to 54. Find the s, p, d, and f electrons.
Write a summary relating first ionization energy to periodicity and list your
conclusions. Are ionization energies periodic in their behavior? In other words,
can they be related to the position elements have on the periodic table?
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All rights reserved.
45
World of Chemistry