SWBAT recognize and explain the reason for the periodic trends of atomic radius, ionization energy, and electronegativity.

Coulombic attraction and atomic structure are responsible for properties of elements, which determines their arrangement on the periodic table.

This lesson addresses the following NGSS standards:

**HS-PS1-1**:*Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms*. Students will be using experimental data to infer the periodic trends for atomic radius, first ionization energy and electronegativity.**Patterns Cross Cutting Concept**:*Graphs, charts, and images can be used to identify patterns in data.***Science and Engineering Practice 2**:*Developing and using models*. Students will use the visual models to determine patterns.

The original POGIL activity for Periodic Trends is fantastic. I have used it to good success with honors students in the past. Last year, I noticed my general chemistry students were confused by the amount of data presented at once.

So I modified the activity this year three ways.

- I broke apart the original model into three sections: Atomic Radius, Ionization Energy, and Electronegativity
- I added an introduction section to review Coulombic attraction.
- I changed the format to a reciprocal learning activity.

In this activity, students become experts on a task by working with peer groups. They then re-group and coach a different group of peers through their expertise, and learn from their peer experts about the other sections. The goal is to make the learning both more social and to encourage good discussion about the topic at hand.

Under the permission from Flinn Scientific, the entire POGIL packet and examples of student work cannot be posted to this site. I strongly recommend it to teachers of chemistry at any level who are looking to incorporate more student thinking and inquiry activities into their classroom.

8 minutes

When the bell rings, I pass out the packet (not posted due to copyright restrictions) and ask students to put their names on it.

I then ask them to work together a table to answer the three review questions on the front of the page.

Students may struggle with this piece. Although it has been a while since we explicitly discussed Coulombic attraction, it has been at the heart of what we've been doing for the past 3 weeks. To break students loose mentally, I provide the following scaffold for question 1 in black marker on the board.

I ask students what happens to the force as the distance changes. Students provide the text in blue, refreshing the relationship between distance between particles and force of attraction.

We then go through a similar process for the second and third questions.

With the last question, we add the positive and minus beneath the term, to refresh for students that whenever they see the word "Coulombic" it means attraction between opposite charges.

Next I point students to the day 1 directions, that they will work with a group on one part of the packet. They need to figure out the information from the model provided, and then figure out how they will coach their peers through their model tomorrow.

I have students move to the lab stations based on the number highlighted at the top of the page by their name. Groups 1 and 4 will work on the Atomic Radius in Model 1, Groups 2 and 5 will work on Ionization Energy in Model 2, and Groups 3 and 6 will work on Electronegativity in Model 3.

25 minutes

Each group has the same basic responsibility:

- Define the property they are exploring.
- Determine the group trend for their property.
- Determine why that group trend exists by connecting atomic structure and the two variables for Coulombic Attraction
- Determine the period trend for their property.
- Determine why that period trend exists by connecting atomic structure and the two variables for Coulombic Attraction

In my modified models, the data is more clearly worked with.

Students only have two numbers, the atomic number and the radius, along with the symbols and scaled valence electron diagrams. That said, students still struggled with understanding the questions and had difficulty identifying the trends in atomic radius.

Students working with Ionization Energy and Electronegativity also had difficulty, but more with the definition of the property itself, not with the trend.

The misunderstandings about the property itself led to issues with connecting the trend to what students already knew about Coulombic attraction.

Originally, I was going to have students stay in the same group to determine their coaching questions. However, seeing some difference in abilities as I walked the room, I deliberately intermixed groups 1 and 4, 2 and 5, and 3 and 6 to ensure I had one confident student in each of the six groups.

Attached is a key for each property group.

17 minutes

After re-organizing students, I had them compare notes about the trends and reasons they had found. By comparing notes and debating areas where they were inconsistent, students got to a better understanding of the reason behind each trend.

Most inconsistencies stemmed from improperly applying the Coulombic attraction rules from the introduction. Students were attributing changes to size of the atom instead of number of protons, and vice versa. Providing students the time to work through their misunderstandings in small groups gave them increased confidence to coach through their section the following day.

While students were working, I circulated the room and helped guide conversations. I was able to be very hands off in this portion of the lesson as most conversations went well on their own. Some students began to disengage, so I did some prompting and encouraging to stick it through. The responsibilities of having to teach this to other students the following day helped students follow through and stay engaged.

Students did not have time to develop a coaching plan, so at the end of the period I collected their packets, and moved the coaching plan to day 2.