Trends in the Periodic Table
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 the atom.
Procedure for Part A:
1. Plot a graph of atomic radius vs. atomic number using the data provided in the table.
Place atomic radius on the VERTICAL axis and atomic number on the HORIZONTAL axis.
2. Join the data points for each element with a straight line.
3. Circle the points at the ‘peaks’ (highest points) and ‘valleys’ (lowest points). Write the
element symbol of the element you circled next to it.
Answer the following questions based on this graph:
1. Which FAMILY of elements corresponds to the ‘peaks’ in your graph of atomic radius?
Where is this family found on the periodic table? (group number)
2. Which FAMILY of elements corresponds to the ‘valleys’ in the graph of atomic radius?
Where is this in the periodic table?
3. What is the trend in atomic radius as the atomic number increases in a family/column of
the periodic table? (increases/ decreases)
4. What is the trend in atomic radius as atomic number increases in a period/row of the
periodic table?
Part B: Trends in Ionization Energy
Procedure:
1. Plot a graph of ionization energy vs. atomic number using the data provided in the table.
Place ionization energy on the VERTICAL axis and atomic number on the HORIZONTAL
axis.
2. Join the data points for each element with a straight line.
3. Circle the points at the ‘peaks’ (highest points) and ‘valleys’ (lowest points). Write the
element symbol of the element you circled next to it.
Answer the following questions based on this graph:
1. Which FAMILY of elements corresponds to the ‘peaks’ in your graph of ionization energy?
Where is this family found on the periodic table? (group number)
2. Which FAMILY of elements corresponds to the ‘valleys’ in the graph of ionization energy?
Where is this in the periodic table?
3. What is the trend in ionization energy as the atomic number increases in a family/column
of the periodic table? (increases/ decreases)
4. What is the trend in ionization energy as atomic number increases in a period/row of the
periodic table?
5. Research and explain what the PERIODIC LAW is. Explain how this law is demonstrated in
the two graphs that you have drawn.
Atomic
Number
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
Element
Hydrogen
Helium
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Sodium
Magnesium
Aluminum
Silicon
Phosphorous
Sulfur
Chlorine
Argon
Potassium
Calcium
Scandium
Titanium
Vanadium
Chromium
Manganese
Iron
Nickel
Copper
Zinc
Gallium
Germanium
Arsenic
Selenium
Bromine
Krypton
Rubidium
Strontium
Element
Symbol
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
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
Rb
Sr
Atomic
Radius (nm)
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
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