Graphing Trends in the Periodic Table
Name: _________________________________
Objective: To understand trends of the periodic table and practice methods of graphing.
Background
The Periodic Table is arranged according to the Periodic Law. The Periodic Law states that when elements are arranged in order of
increasing atomic number, their physical and chemical properties show a periodic pattern. Students can discover these patterns by
examining the changes in properties of elements on the Periodic Table. The properties that will be examined in this lesson are: atomic
radius AND first ionization energy
1. Make a prediction as to what will happen to the sizes of atoms as one progresses from left to
right across a period on the periodic table. (Example: the sizes of atoms will (increase, decrease,
remain constant) as one goes left to right across a period.)
2. According to your prediction, make a sketch of how you would EXPECT a graph to appear if you plotted atomic
number on the X-axis and atomic radius (size of the atom) on the Y-axis.
Procedure:
Graph the following information according to the steps described
Graph 1: Atomic Radius vs Atomic Number: Elements 3-20
For elements 3-20 make a graph of atomic radius as a function of atomic number. Plot atomic number on the X axis and atomic radius
on the Y axis. After creating the graph, use a colored pen or pencil to draw a vertical line that represents that beginning of each period
(horizontal row on the periodic table).
Graph 2: Atomic Radius vs Atomic Number: Groups IA and IIA
For elements in Group 1 (Alkali metals), make a graph of atomic radius as a function of atomic number. Make a second line on this
same graph that will represent Group 2 (Alkaline Earth Metals). Use a periodic table to determine which elements are members of
Group 1 and which elements are members of Group 2.
Graph 3: Ionization Energy vs Atomic Number: Elements 3-20
For elements 3-20, make a graph of the energy required to remove the easiest electron (first ionization energy) as a function of atomic
number. Plot atomic number on the X axis and energy required on the Y axis. After creating the graph, use a colored pen or pencil to
draw a vertical line that represents that beginning of each period (horizontal row on the periodic table).
Graph 4: Ionization Energy vs Atomic Number: Groups IA and IIA
For elements of Group 1 (Alkali metals), make a graph of the energy required to remove the easiest electron (first ionization energy)
as a function of atomic number. On the same graph make a second line to represent Group 2 (Alkaline Earth Metals). Use a periodic
table to determine which elements are members of Group 1 and which elements are members of Group 2.
Symbol
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
Rb
Sr
Cs
Ba
Atomic
Number
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
37
38
55
56
Atomic
Radius
1.23
0.89
0.8
0.77
0.7
0.66
0.64
0.67
1.57
1.36
1.25
1.17
1.1
1.04
0.99
0.98
2.03
1.74
2.16
1.91
2.35
1.98
First
Ionization
Energy
124
215
191
260
335
314
402
497
119
176
138
188
242
239
299
363
100
141
96
131
90
120
Analysis:
1. Record any similarities and differences between your predicted graph and the graph
of actual data.
2. What does happen to the sizes of atoms as one goes left to right across a period?
3. What does happen to the sizes of atoms as one goes down a group?
4. Looking at the Bohr models of atoms, offer an explanation as to WHY the atomic
size changes as it does for both periods and groups.
Periods:
Groups:
5. What happens to the ionization energy as one goes left to right across a period?
6. What happens to the ionization energy as one goes down a group?
7. Offer an explanation as to WHY the ionization energy changes as it does for both
periods and groups.
Period:
Group:
8. What PROPERTIES of elements visibly show periodic trends when their values are
graphed?
Atomic Radius vs Atomic Number: Elements 3 – 20
3.2
3
2.8
2.6
2.4
2.2
2
1.6
1.4
1.2
1
0.8
0.6
0.4
Atomic Number (#)
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
0.2
1
Atomic Radii (picometers)
1.8
Atomic Radius vs Atomic Number: Group IA and IIA
3.2
3
2.8
2.6
2.4
2.2
2
1.6
1.4
1.2
1
0.8
0.6
0.4
Atomic Number (#)
55
50
45
40
35
30
25
20
15
10
3 6 9 12 15 18 21 24 27 30 33 36 39 40 43 46 49 52 55 58
60
0.2
5
Atomic Radii (picometers)
1.8
Ionization Energy vs Atomic Number Elements 3-20
400
380
360
340
320
300
280
240
220
200
180
160
140
120
100
80
60
40
Atomic Numbe r (#)
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
20
1
Ionization Energy
(kJ/mol)
260
Ionization Energy vs Atomic Number: Group IA and IIA
340
320
300
280
240
220
200
180
160
140
120
100
80
60
40
Atomic Number (#)
60
55
50
45
40
35
30
25
20
15
0
10
20
5
Ionization Energy
(kJ/mol)
260