1. No category

9
Why Do They Call It a Periodic Table?
Why Do They Call It a Periodic Table?
Investigating and Graphing Periodic Trends
Have you ever wondered why chemists call that big chart that contains all of the elements, the periodic
table? For years scientists attempted to find some order to the elements that they knew existed. They
looked at various properties and tried out many arrangements. You are going to attempt a similar task.
You will be given a set of cards that contain certain properties. Without referring to the actual periodic
table you will attempt to put the cards in some order that makes sense to you. You will be asked to
explain your reasoning to your classmates.
PURPOSE
In this activity you will graph various periodic properties to ascertain the order. In so doing, you will
see the trends of the periodic table of the elements.
MATERIALS
sets of periodic trend cards
tape
graph paper or computer as teacher instructs
scissors
extra paper
At Home Preparation
Cut along the lines of the periodic trends cards. Try to arrange them in an order. Try several different
patterns to see which makes the most sense to you. When you have an arrangement that you like, tape
them in order to a piece of paper. Justify your arrangement on the student answer page.
334
Laying the Foundation in Middle Grades Chemistry and Physics
Why Do They Call It a Periodic Table?
Atomic Mass
1
Melting Point (oC)
-259
Boiling point (oC)
-252
O in oxide
0.5
Cl in chloride
1
Electronegativity
2.1
Ionization Energy
13.6
Atomic Mass
27
Melting Point (oC)
659
Boiling point (oC)
2327
O in oxide
1.5
Cl in chloride
3
Electronegativity
1.6
Ionization Energy
6.0
Atomic Mass
23
Melting Point (oC)
97
Boiling point (oC)
889
O in oxide
0.5
Cl in chloride
1
Electronegativity
0.9
Ionization Energy
5.1
Atomic Mass
31
Melting Point (oC)
44
Boiling point (oC)
280
O in oxide
2.5
Cl in chloride
3
Electronegativity
2.1
Ionization Energy
10.5
Atomic Mass
19
Melting Point (oC)
-218
Boiling point (oC)
-188
O in oxide
0.5
Cl in chloride
1
Electronegativity
4.0
Ionization Energy
17.4
Atomic Mass
16
Melting Point (oC)
-219
Boiling point (oC)
-183
O in oxide
-Cl in chloride
2
Electronegativity
3.4
Ionization Energy
13.6
Atomic Mass
39
Melting Point (oC)
64
Boiling point (oC)
757
O in oxide
0.5
Cl in chloride
1
Electronegativity
0.8
Ionization Energy
4.3
Atomic Mass
14
Melting Point (oC)
-210
Boiling point (oC)
-196
O in oxide
2.5
Cl in chloride
3
Electronegativity
3.0
Ionization Energy
14.5
Periodic Trend Cards
Atomic Mass
36
Melting Point (oC)
-101
Boiling point (oC)
-34
O in oxide
0.5
Cl in chloride
1
Electronegativity
3.2
Ionization Energy
10.4
Atomic Mass
40
Melting Point (oC)
-189
Boiling point (oC)
-186
O in oxide
-Cl in chloride
-Electronegativity
-Ionization Energy
15.8
Atomic Mass
12
Melting Point (oC)
3470
Boiling point (oC)
4347
O in oxide
2
Cl in chloride
4
Electronegativity
2.6
Ionization Energy
11.3
Atomic Mass
11
Melting Point (oC)
2037
Boiling point (oC)
2527
O in oxide
1.5
Cl in chloride
3
Electronegativity
2.0
Ionization Energy
8.3
Laying the Foundation in Middle Grades Chemistry and Physics
Atomic Mass
9
Melting Point (oC)
1287
Boiling point (oC)
2507
O in oxide
1
Cl in chloride
2
Electronegativity
1.6
Ionization Energy
8.3
Atomic Mass
7
Melting Point (oC)
179
Boiling point (oC)
1327
O in oxide
0.5
Cl in chloride
1
Electronegativity
1.0
Ionization Energy
9.3
Atomic Mass
4
Melting Point (oC)
-272
Boiling point (oC)
-269
O in oxide
-Cl in chloride
-Electronegativity
-Ionization Energy
24.6
Atomic Mass
28
Melting Point (oC)
1407
Boiling point (oC)
2677
O in oxide
2
Cl in chloride
4
Electronegativity
1.9
Ionization Energy
8.2
9
Atomic Mass
20
Melting Point (oC)
-248
Boiling point (oC)
-246
O in oxide
-Cl in chloride
-Electronegativity
-Ionization Energy
21.6
Atomic Mass
32
Melting Point (oC)
119
Boiling point (oC)
445
O in oxide
3
Cl in chloride
2
Electronegativity
2.6
Ionization Energy
10.4
Atomic Mass
40
Melting Point (oC)
851
Boiling point (oC)
1487
O in oxide
1
Cl in chloride
2
Electronegativity
1.0
Ionization Energy
6.1
Atomic Mass
24
Melting Point (oC)
650
Boiling point (oC)
1117
O in oxide
1
Cl in chloride
2
Electronegativity
1.3
Ionization Energy
7.6
335
9
Why Do They Call It a Periodic Table?
PROCEDURE
1. Compare your arrangement with your classmates’ results. Are there differences? Are there
similarities? If there are differences, try to resolve them.
2. Now your teacher will give you the atomic number and the symbol for each of your cards. Work
with your partner to arrange the cards in order of atomic number.
3. Use two sheets of graph paper. Label each “Trends in Chemical Properties”. Label the x-axis
“Atomic Numbers” and number it from 1 to 20. One of you should label your y-axis “Oxygen atoms
per atom of element”. The other should have the y-axis labeled “Chlorine atoms per atom of
element”. Determine a proper scale for each. Construct a bar graph for each.
4. Get two more sheets of graph paper. Label one “Boiling Points vs. Atomic Number”. Label the
other “Melting Points vs. Atomic Number”. Number the x-axes with atomic numbers from 1 to 20
as before. Determine an appropriate scale for the temperatures along the y-axes. Do not graph
element #6. Construct bar graphs for each.
5. Construct two more graphs. Label one “Ionization Energy vs. Atomic Number”. The units for
ionization energy are kJ/mol. Be sure to include the units on your graph. The other should be
labeled “Electronegativity vs. Atomic Number”. Electronegativity is a relative number and has no
units. As you did before, label the x-axis “Atomic Number” and scale from 1 to 20. Use a line
graph to plot these properties. Look at all six graphs, and answer the conclusion questions.
336
Laying the Foundation in Middle Grades Chemistry and Physics
Why Do They Call It a Periodic Table?
9
Name _____________________________________
Period ____________________________________
Why Do They Call It a Periodic Table?
Investigating and Graphing Periodic Trends
JUSTIFICATION OF ARRANGEMENT
Explain why you arranged the cards in the particular order that you chose.
DATA AND OBSERVATIONS
Include your graphs with your report.
ANALYSIS AND CONCLUSION QUESTIONS
1. Compare the following graphs. Do any of the graphs show a repeating, or cyclic, pattern? Focus on
elements with very large or very small values.
a. Oxygen atoms vs. atomic number and Chlorine atoms vs. atomic number
Laying the Foundation in Middle Grades Chemistry and Physics
337
9
Why Do They Call It a Periodic Table?
b. Melting point vs. atomic number and Boiling point vs. atomic number
c. Electronegativity vs. atomic number and Ionization energy vs. atomic number
338
Laying the Foundation in Middle Grades Chemistry and Physics
Why Do They Call It a Periodic Table?
9
2. Are these graphs consistent with patterns found in your earlier grouping of elements? Explain.
3. Based on your graphs, why is the chemist’s organization of elements called a Periodic Table?
4. Where are the elements with the highest oxide numbers located on the Periodic Table? How about
the elements with the highest chloride numbers?
5. Predict which element should have the lowest boiling point: selenium (Se), bromine (Br), or krypton
(Kr)? Explain your prediction.
6. Which should have the lowest ionization energy: rubidium (Rb) or cesium (Cs)? Explain your
prediction.
7. Which would have the greatest ionization energy: antimony (Sb) or tellurium (Te)? Explain your
prediction.
Laying the Foundation in Middle Grades Chemistry and Physics
339