Download Chem Activity: Polyatomic Ions

ChemActivity: Periodic Trends
Information: The Periodic Table arranges the elements in regular, repeating patterns. These patterns reflect the
arrangement of electrons and are the driving force behind the physical and chemical properties of the elements.
In this activity you will investigate the structure of the Periodic Table and the trends in atomic radius, ionization
energy, electronegativity, and ion radius
1. Go to the Chemistry group in Edmodo. In the news feed open the spreadsheet “ChemActivity Periodic
Trends.” Select the “atom properties” tab from the bottom navigation bar.
2. Take out a Periodic Table. Refer to it as you investigate group and period properties.
Model Set 1: Atomic Radius
1. Use a textbook to find the definition of atomic radius and write the definition below.
2. In the spreadsheet, the column to the right of the graph has buttons to select which graph you want to
analyze. Select ATOMIC RADIUS.
3. One at a time, enter the atomic number for each Group 1 element in the yellow box to observe its atomic
radius (see image below). A blue box will appear around the point on the graph corresponding to that
element.
What seems to be happening to the atomic radius within the elements in this group?
4. Repeat this procedure for Groups 2, 13, 14, 15, 16, 17, and 18. What happens to the atomic radius as you go
down any of these groups?
5. Now, starting with lithium, investigate what happens to the atomic radius as you proceed across Period 2.
Repeat this procedure for Period 3. What is the general trend that occurs as you go from left to right across
the period?
6. Repeat this procedure for Period 4. What is different in the trend for this period? In which section of the
Periodic Table do these differences occur?
Model Set 2: Ionization Energy
1. Use a textbook to find the definition of ionization energy and write the definition below.
2. Select 1st Ionization Energy from the list to the right of the graph in the spreadsheet. This is a graph of
ionization energy vs. atomic number. Investigate what happens to the ionization energy within each group
as you did in steps 3 and 4 in Model Set 1. What is the general trend in ionization energy as you go down a
group?
3. Now investigate what happens to the ionization energy within a period. For this step, only investigate the
ionization energy for Groups 1, 2, 13, 14, 15, 16, 17, and 18 within Periods 1-4. What is the general trend in
ionization energy as you move from left to right across a period?
Model Set 3: Electronegativity
1. Use a textbook to find the definition of electronegativity and write the definition below.
2. As you did in Model Sets 1 and 2, investigate the general trend in electronegativity as you go down a group
(DO NOT INCLUDE GROUP 18). What is the general trend in electronegativity value within the elements
in a particular group?
3. As you did in Model Sets 2 and 3, investigate the general trend in electronegativity as you go across a
period (DO NOT INCLUDE GROUP 18). What is the general trend in electronegativity value within the
elements in a particular period?
Model Set 4: Ion Radius
1. Use the textbook to define the terms “cation” and “anion.”
2. Click on the “ion properties” tab in the spreadsheet and then click on “add cations.” Compare the size of the
cations to the neutral atoms.
3. Uncheck the “add cations” box and click on “add anions.” Compare the size of the anions to the neutral
atoms.
4. Why do you think these size relationships exist, i.e. why is the relative size of a cation compared to the
neutral atom always the same? Why is the relative size of an anion to the neutral atom always the same?
(Hint: How do you make a cation? An anion?)
Self-Check
1. What happens to the size of atoms as the atomic number increases within a period?
2. What happens to the size of atoms as the atomic number increases within a group?
3. What is the relationship between the trend in atomic radius and the trend in ionization energy?
4. What is the relationship between the trend in atomic radius and the trend in electronegativity?