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Red Lion Area Senior High Chemistry Department
Physical and Chemical Property Patterns for Elements
Standard: 3.1.12.C
Part I: Grouping the Elements
Access the 20 element data cards by clicking here. YOU MUST ARRANGE THE CARDS IN INSPIRATION.
Each card lists some properties of one of the first 20 elements.
1. Arrange the cards into groups of elements with similar properties.
2. Within each group, arrange the elements in order of increasing atomic mass.
3. Decide on the most useful and logical pattern within and among the card groups.
4. Use arrows from the menu, indicating how you arranged the elements.
5. When your group has completed the above exercise, each member should individually write 2-3 sentences on his
or her notebook paper explaining how the cards were arranged and why you decided to use that particular
arrangement. PRINT ONE COPY FOR EACH GROUP MEMBER. BE SURE TO PUT THE NAMES OF ALL
GROUP MEMBERS ON THE DOCUMENT.
READ THE FOLLOWING BEFORE MOVING ON TO PART II:
Early periodic tables offered no explanation for similarities found among element properties. The reason for these
similarities was discovered about 50 years later. It serves as the basis for the modern periodic table.
Recall that all atoms are composed of smaller particles including equal numbers of positively charged protons and
negatively charged electrons. One essential difference discovered later among atoms of different elements is their
number of protons, a value called the atomic number. Every sodium atom contains 11 protons; the atomic number
of sodium is 11. Each atom of carbon contains 6 protons. If the number of protons in an atom is 9, it is a fluorine
atom. If it is 12, it is an atom of magnesium. In short, knowing the atomic number or the number of protons
allows us to identify which element it represents. All elements are in sequence according to their atomic numbers
in the modern periodic table.
In the next exercise, you will draw graphs to explore the relationship between atomic number and element
properties.
Part II: Graphing Properties
Number your elements 1-20. Use the atomic number and information on the element card to make four graphs.
Each person must make his or her own graphs. Use Excel to create your graphs. When you are finished you should
have a total of TWO graphs containing the following: Graph I: Atomic number vs. Ratio of N/M for O, Atomic
number vs. Ratio of N/M for Cl, Graph II: Atomic number vs. attraction to electrons, and Atomic number vs.
atomic radius.
GRAPH I: Trends in a Chemical Property
1. Label the x axis with atomic numbers from 1 to 20.
2. On the y axis, set up your axis accordingly based upon the range of the ratios.
3. Plot the ratio of N/M for each element on the y-axis (you should have two lines).
Graph II: Trends in a Physical Property
1. Label the x axis with the atomic numbers from 1 to 20.
2. On the y axis, select either attraction to electrons or atomic radius from the data cards and set up your axis
accordingly.
3. Plot the data from the cards.
4. Repeat for the other pattern, giving you two lines.
For each graph, use the graphing checklist provided to make sure your graph contains all the necessary parts!!!
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graph takes up at least two thirds of the page
graph has an appropriate title (top center)
axes are labeled properly
axes contain units in parenthesis
points are placed on graph correctly
lines are neatly drawn (key or legend included if needed)
scales are numbered correctly (i.e. 5, 10, 20, 50, etc.)
scales are uniform (i.e. 1 block = 10 units for the entire scale)
pencil is used (ink may be used if rough copy is included)
overall neatness of graph
score = _________________/ 5
Part III: Questions about the Graphs ~ Each person must write his or her own answers to the questions.
1. Do the graphs reveal a repeating or cyclic pattern? Explain. (2 points)
2. Are these graphs consistent with your earlier grouping of the elements on the construction paper? Why or why
not? (2 points)
3. Based on these graphs, why is the chemists organization of elements called a periodic table? (3 points)
READ THE FOLLOWING BEFORE MOVING ON TO PART IV:
When elements are listed in order by their atomic numbers and grouped according to similar properties, they form
seven horizontal rows called periods. Each vertical column in the table contains elements with similar properties.
These are called groups or families. The alkali metal family for example consists of the six elements in the first
column at the left side of the table. These elements are all highly reactive metals. They react with chloride on a
1:1 ratio to form compounds like LiCl and NaCl. They react with oxygen in a 2:1 ratio to form compounds such as
Li2O and Na2O. All of the chloride and oxide compounds formed by the alkali metal family are ionic. By contrast,
the noble gas family in the far right column of the table consists of unreactive elements. Only xenon and krypton
are known to form any compounds at all.
The arrangement of elements in the periodic table provides an orderly summary of the key characteristics of
elements. If we know the major properties of a certain chemical family, we can predict some of the behavior of
any element in that family.
Some properties of an element can be estimated by averaging the properties of the elements located just above and
just below the element in question. This is how Dimitri Mendeleev (1834-1907), publisher of the first useful
periodic table, predicted the properties of elements unknown in his time. He was so certain about his conclusions
that he left gaps in his periodic table for missing elements with predictions of their properties. When these
elements were eventually discovered, they fit in exactly as expected. Mendeleevπs fame rests largely on the
correctness of these predictions.
As an example, suppose that krypton (Kr) is an unknown element. Estimate the boiling point of krypton given
that the boiling point for argon under similar conditions is ≠186 C and for xenon is ≠112 C. In its group on the
periodic table, krypton is preceded by argon and followed by xenon. Taking the average of the boiling points of
these elements gives:
[(-186 C) + (-112 C)] / 2 = -149 C.
The estimated boiling point for krypton is ≠149 C. The actual boiling point for krypton is ≠157 C. The periodic
table has helped guide us to a useful prediction.
Formulas for chemical compounds can also be predicted using the periodic table. Carbon and oxygen form carbon
dioxide (CO2). What formula would you predict for a compound of carbon and sulfur? Since oxygen and sulfur
are in the same column, they will react with carbon in the same ratios. The best guess for carbon and sulfur would
be CS2 and this is a correct prediction!
Part IV:
Using the Periodic Table to Predict Properties
1. One element undiscovered in Mendeleevπs time was germanium (Ge). Given the information that the melting
points of silicon (Si) and tin (Sn) are 1410 C and 232 C respectively, estimate the melting point of germanium. (2
points)
2. Estimate the melting point of rubidium (Rb). The melting points of potassium (K) and cesium (Cs) are 64 C
and 29 C respectively. (2 points)
3. Would you expect the melting point of sodium (Na) to be higher or lower than that of rubidium? (2 points)
4. Here are formulas for several known compounds:
NaI
MgCl2
CaO
Al2O3
CCl4
Using that information, predict the formula of a compound formed from: (1 point each)
a. C and F
b. Al and S
c. K and Cl
d. Ca and Br
e. Ba and O
5. Which family of elements is so lacking in chemical reactivity that its elements were originally regarded as inert?
(2 points)