Understanding the Periodic Trends
Chemistry Lab
Purpose: To know how to use the periodic table to identify trends in ionization energy, electronegativity,
and the sizes of ions and atoms.
Introduction
The Periodic Table is arranged according to 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. This is periodicity! You can discover these patterns by examining the changes in properties of
elements on the Periodic Table. The properties that will be examined in this activity are electronegativity,
atomic radius and 1st ionization energy.
Procedure:
1. Draw a data table like the one below. Add a title! Make each box large enough to add data.
H
Li
Na
Mg
Al
Si
P
S
Cl
Ar
186 pm
496kJ/mol
0.9
K
Rb
Cs
2. On your laptop, navigate to http://www.chemicool.com/ OR http://www.ptable.com/.
Click on an element symbol to learn more about that element!
3. Find the trend information for each element above and list under the symbol (in this order) the atomic
radius, 1st ionization energy, and electronegativity. Highlight the atomic radius yellow, the 1st ionization
energy green, and the electronegativity blue. Sodium is completed for you.
Analysis/Discussion
1. Define atomic radius, ionization energy, and electronegativity.
2. Copy and complete the statements for trends across a period: Choose increase or decrease.
 Across a period () atomic radius tends to _____________________________.
 Across a period () first ionization energy tends to _________________________.
 Across a period () electronegativity tends to _____________________________.
2. Copy and complete the statements for trends down a group:
 Down a group () atomic radius tends to ________________________________.
 Down a group () first ionization energy tends to ___________________________.
 Down a group () electronegativity tends to _______________________________.
3. Rank the following element from highest to lowest electronegativity: argon, arsenic, barium, sulfur, tin
4. Rank the elements in #3 from smallest to largest radius.
5. Ranks the elements in #3 from lowest to highest ionization energy.
Conclusion: Summarize what you learned about periodicity and the periodic trends.