Trends in the Periodic Table
Title page
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Neat & Organized… preferably typed
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Observations
Graph of part 1 (atomic radii) data
Graph of part 2 (ionization energies) data
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Analysis Questions
Part 1- atomic radii
#1- group name for peaks, include main group #
#2- group name for troughs, include main group #
#3- trend within the group
#4- trend across a period
#5- predict atomic radius for Co, I, Cs
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Part 2- Ionization Energies
#1- group name for peaks, include main group #, compare to part 1
#2- group name for troughs, include reasoning
#3- trend within a group
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#4- trend across a period
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#5- predict first ionization energy for Co, Xe, Cs
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#6- periodic law
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Summary/Conclusion- include periodic law in answer.
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TRENDS IN THE PERIODIC TABLE
Introduction:
Numerical data about the structure, size and ionization energy of the first 38 elements as listed
in Table 8.1 on the next page. Regularities in variations of these properties will be analyzed
with the help of graphs. The purpose is to plot and interpret graphical data of trends in the
periodic table, and to predict behavior of elements based on these trends.
Part A: Trends in the Size of Atoms
To examine whether there is a pattern in the relationship between the size of an atom and its
atomic number you will plot graphs of the atomic radius of each atom against its atomic
number. Although an atom does not have an exact size, it is possible to determine the distance
between the nuclei of adjacent atoms in a molecule. These distances can be used to obtain
atomic radii which gives a reasonable approximation of the size of an atom. Hence, each atom
is thought of as being a sphere with a measurable radius.
Procedure:
1. Plot a graph of atomic radius vs. atomic number using the data provided in Table 8.1.
Place atomic radius on the vertical axis, and atomic number on the horizontal axis.
2. Join the datum point for each element with a straight line. If the datum point for a
particular element is missing, use a broken line to join the datum points for adjacent
elements.
3. Circle those points at the ‘peaks’ and ‘valleys’, and write the symbol of these
corresponding elements beside the circles.
Analysis Questions for Part A
1. Which family of elements corresponds to the ‘peaks’ in the plot of atomic radii? Where
is this family of elements found on the periodic table (include group #)?
2. Which family of elements corresponds to the ‘valleys’ in the plot of atomic radii?
Where is this family of elements found on the periodic table?
3. Describe the trend in atomic radius as atomic number increases in a family or column
of the periodic table.
4. Describe the trend in atomic radius as atomic number increases in a period or row of
the periodic table.
5. Based on the trends revealed on the graph, estimate the atomic radius of 27Co, 53I, and
55Cs
Part B: Trends in the First Ionization Energy
The energy required to remove an outermost electron from an atom is the first ionization
energy.
Procedure:
1. Plot a graph of first ionization energy vs. atomic number using the data provided in
Table 8.1. Place ionization energy on the vertical axis, and atomic number on the
horizontal axis.
2. Join the datum point for each element with a straight line. If the datum point for a
particular element is missing, use a broken line to join the datum points for adjacent
elements.
3. Circle those points at the ‘peaks’ and ‘valleys’, and write the symbol of these
corresponding elements beside the circles.
Analysis Questions for Part B
1. Which family of elements corresponds to the ‘peaks’ in the plot of first ionization
energy? Where is this family of elements found on the periodic table (include group
#)?
2. Which family of elements corresponds to the ‘valleys’ in the plot of first ionization
energy? Where is this family of elements found on the periodic table?
3. Describe the trend in first ionization energy as atomic number increases in a family or
column of the periodic table.
4. Describe the trend in first ionization energy as atomic number increases in a period or
row of the periodic table.
5. Based on the trends revealed on the graph, estimate the first ionization energy of 27Co,
54Xe, and 55Cs
6. State the periodic law.
*Be able to explain how the periodic law is demonstrated by both the trends in atomic
radius and first ionization energy in your summary/ conclusion.
Table 8.1: Atomic Radii and First Ionization Energies of the First 38 Elements
Atomic
Number
Element
Symbol
Mass
Number
Number
of
Neutrons
Atomic
Radius
(nm)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
Hydrogen
Helium
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Flourine
Neon
Sodium
Magnesium
Aluminum
Silicon
Phosphorus
Sulfur
Chlorine
Argon
Potassium
Calcium
Scandium
Titanium
Vanadium
Chromium
Manganese
Iron
Cobalt
Nickel
Copper
Zinc
Gallium
Germanium
Arsenic
Selenium
Bromine
Krypton
Rubidium
Strontium
H
He
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
Rb
Sr
1
4
7
9
11
12
14
16
19
20
23
24
27
28
31
32
35
40
39
40
45
48
51
52
55
56
59
59
64
65
70
73
75
79
80
84
85
88
0
2
4
5
6
6
7
8
10
10
12
12
14
14
16
16
18
22
20
20
24
26
28
28
30
30
32
31
35
35
39
41
42
45
45
48
48
50
0.032
0.031
0.123
0.089
0.082
0.077
0.075
0.073
0.072
0.071
0.154
0.136
0.118
0.111
0.106
0.102
0.099
0.098
0.203
0.174
0.144
0.132
0.122
0.118
0.117
0.117
--0.115
0.117
0.125
0.126
0.122
0.120
0.117
0.114
0.112
0.216
0.191
First
Ionization
Energy
(eV)
13.6
24.5
5.4
9.3
8.3
11.3
14.5
13.6
17.4
21.6
5.1
7.6
6.0
8.1
10.5
10.4
13.0
15.8
4.3
6.1
6.5
6.8
6.7
6.8
7.4
7.9
--7.6
7.7
9.4
6.0
7.9
9.8
9.8
11.8
14.0
4.2
5.7