Download LAB 4 - Valley Catholic School

Name ____________________________________
Period: _____
Lab Partners: ______________________________
Date _________________
LAB 4.5: Periodicity
Purpose: To graph properties of elements on the periodic table to see how they relate to
the atomic number
Background information: Atomic radius is the radius of the neutral atom. Ionization
energy is the energy needed to pull away the outermost electron to an infinite distance
from the atom.
Materials:
 Data for physical properties of elements
 Computer with graphing program or graph paper
Data table:
Atomic
Number
Atomic
Radius (Å)
1
2
3
4
5
0.53
0.31
1.67
1.12
0.87
Ionization
Energy
(kJ/mol)
1312.0
2372.3
520.2
899.5
800.6
6
7
8
9
10
11
12
13
14
0.67
0.56
0.48
0.42
0.38
1.90
1.45
1.18
1.11
1086.5
1402.3
1313.9
1681.0
2080.7
495.8
737.7
577.5
786.5
15
16
17
18
19
0.98
0.88
0.79
0.71
2.43
1011.8
999.6
1251.2
1520.6
418.8
20
1.94
589.8
Data source: http://www.webelements.com/atoms.html downloaded 07 Jan 2009
Copyright © 2009 by Kendall Hunt Publishing Company
Page 1 of 4
LAB 4.5: Periodicity
Procedure:
For graph paper:
1. Make a graph with the atomic number along the x axis and the atomic radius along the
y axis. Connect the data points in a “connect-the-dots” style. We’re using this method
instead of a best-fit line method because we want to see the trend of how the variables
change, rather than find an average change. Remember to use as much of the paper as
possible—stretch out the axis.
2. Make a similar graph with the atomic number along the x axis and the ionization
energy along the y axis.
For computer graphing:
1. Open the graphing/spreadsheet program on the computer (Microsoft Excel or other
program as designated by your teacher).
2. Spreadsheets are organized with columns labeled with letters and rows labeled with
numbers. Each cell is named with the letter and the number (cell 1A is in row 1 and
column A).
3. Enter the following labels into cells 1A–1C: atomic number, atomic radius, ionization
energy.
4. Fill in the spreadsheet with the data provided.
5. Highlight the block of cells in columns A and B with data (including the labels in row
1).
6. Insert and format the chart. Use the following instructions for Microsoft Excel.
7. From the Insert menu, choose Chart.
8. Select XY (Scatter).
9. Choose the type that has data points marked with straight lines connecting the data
points (connect-the-dots style). Again, we’re using this type of graphing instead of a
best-fit line because we are specifically looking for trends—how the values rise and fall
as the atomic number changes, not the overall average of the values.
10. Select “Chart Tools” and “Layout”. Select “Axis Titles” and enter the correct titles
for both the Primary Horizontal (“Atomic Number” as the x-axis label) and Primary
Vertical axis (“Atomic Radius” as the y-axis label).
11. Select “Chart Title” and type “Periodic trends” as the chart title (also put your name
in the title so that we know whose printout is whose).
12. Print a graph for each member of the group.
13. Repeat steps 5–12 for the cells with data in columns A and C. To highlight columns
that are not next to each other, highlight column A, then hold the control button down
while highlighting column C. The Primary Vertical axis should be labeled “Ionization
Energy).
Copyright © 2009 by Kendall Hunt Publishing Company
Page 2 of 4
LAB 4.5: Periodicity
Discussion
1. Atomic radius:
a. As you move from left to right across the periodic table (for example, look at
elements 11–18), what happens to the atomic radius?
b. Is the trend fairly smooth, or is it spiky?
c. As you move down the periodic table (for example, look at elements 3, 11, and 19),
what happens to the atomic radius?
d. Is the trend fairly smooth, or is it spiky?
2. Ionization energy:
a. As you move from left to right across the periodic table (for example, look at
elements 11–18), what happens to the ionization energy?
b. Is the trend fairly smooth, or is it spiky?
c. As you move down the periodic table (for example, look at elements 3, 11, and 19),
what happens to the ionization energy?
Copyright © 2009 by Kendall Hunt Publishing Company
Page 3 of 4
LAB 4.5: Periodicity
d. Is the trend fairly smooth, or is it spiky?
3. Both trends:
a. Put the atomic radius graph on top of the ionization energy graph. Hold them up to
the light so that you can see both at the same time. What do you notice about how
they compare to each other?
b. Based on your last question, are atomic radius and ionization energy directly or
indirectly related?
c. Give a reason why you might think that they’re related in the way that they are.
How might the radius of the atom affect the amount of energy needed to pull off the
outermost electron?
Copyright © 2009 by Kendall Hunt Publishing Company
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