Periodic Trends- Reciprocal Style Day 2

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

Big Idea

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


This is Day 2 of this lesson.  Day 1 can be viewed here.

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 ConceptGraphs, 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.
On Day 1, students became experts on a specific periodic property by working with peer groups. 
Today they 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.
Not all classes were able to proceed with the activity.  The "Alternative Option" at the end of the lesson addresses this.

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.


Group Work- Developing a Coaching Plan

14 minutes

When students enter the room, they are directed straight into their number groups.  I tell the students they have 4 minutes to review the material, and 8 minutes to create a Q and A to help guide their coaching of classmates.

While students are working, I am circulating the room to clarify any final confusions.  I also put the teaching schedule on the board with appropriate times

  • Atomic Radius- 12 minutes  __:__ - __:__
  • Ionization Energy- 12 minutes  __:__ - __:__ 
  • Electronegativity- 12 minutes  __:__ - __:__

When time is up, I put the students into their teaching and learning groups.  Each teaching and learning group has one student from each property present.

For example, Group 1 has student A from the atomic radius group, student A from the ionization energy group, and student A from the electronegativity group.  Group two has student B from each group, and Group 3 has student C from each group.  This is repeated until the whole class is in groups of 3, with each periodic property represented.

I pre-assigned the groups the night before to put students with someone they are comfortable with.  I had a lot of flexibility since I have at least 8 student options for each part of each group.  I direct the students to their table, and start the time for the atomic radius instruction.

Reciprocal Teaching

36 minutes

The leader for atomic radius leads the group through this section of the activity at each table.  While the other two students work through, the leader provides help and clarification as needed.  For example:

  • G:  "What exactly is atomic radius?"
  • L:  "Its the size of the atom, and the measurements are below the pictures of the atom"


  • G:  "I see it gets smaller across the period, but I don't know why?"
  • L:  "Is it getting more or less attractive if the electrons are closer?  What is making the nucleus more attractive?"
  • G:  "They get a higher atomic number, so more protons?"
  • L:  "Yes"

When students are ready to move on, they can begin the ionization energy section, with the role of leader shifting.  I circulate the room listening for explanations, and making myself available if a leader gets stuck and can't find the words they are looking for. 

I am also making certain that the leader is not just telling the answers or letting his group copy off of him.  When I see this behavior, I correct it and get them back into the roles of the activity.

This continues through the electronegativity section, and then students turn in the packet at the end of the period.

Due to variances in group progress, there was not time for an exit ticket or mini-assessment.  From grading the student packets, it seemed like the activity went well.  Most students had all the sections complete and correct, and their answers varied slightly from their property leader, indicating they did not copy.  Students continued to struggle connecting the periodic trends to the structure of the atom.  They readily recognized the patterns in the property data, but had a hard time discerning why this is the case.

Our unit exam did not show any differences between the class who went through the full reciprocal teaching model and those who I modified.  This could be a failure of the exam (being newly written this year) or indicative that the instruction didn't stick as well as I would have hoped from students engaging and then teaching the material.  We didn't have enough questions on each property to assess if a student excelled on the property in which they led, vs the properties they only engaged as a learner.

Alternative Option

In three of my four classes, there were significant numbers of students who did not complete their work on Day 1, had significant misconceptions still, or where I had significant absences on both Day 1 and Day 2 which would have impacted student groupings.  I was able to combat this two ways:

  1. Whole class completion of the Periodic Trends packet, with the students who completed each section leading the discussion
  2. Periodic Trends PowerPoint

In reviewing the student work at the end of Day 1, I realized I needed to be careful.  While I prize students doing the work and explaining, I can not have them explaining concepts incorrectly.  Ordinarily, I would take an extra day and work with the students who had the misconceptions or who did not do the activity. 

This year, I was 2-7 days behind some of my colleagues in the curriculum, and needed to move on after today.  Those factors collided to run three periods very differently to ensure all students had access to accurate content.

In my first class, we completed the POGIL on the document camera, with me reading the questions aloud and asking the students who worked on it the day before to provide answers.  I called on students by name as I knew who had completed the work and could provide answers.  If students from other groups wanted to volunteer their answers as we went through, I allowed them to do so.

In my afternoon classes, I went through the PowerPoint and instructed students to take notes in their binder.    With each property, I followed the same steps as the POGIL activity: 

  • define the property
  • assess the group trend from pictures or data
  • explain the reasoning behind the trend
  • assess the period trend from pictures or data
  • explain the reasoning behind the trend

However, I did stop after the ionization energy information to demonstrate that property using the alkali metals in the fume hood.  For safety, I only perform these reactions in the fume hood as the evolution of hydrogen in the reactions can be explosive, showering the area with sodium hydroxide.  I ensure students are a safe distance back just in case any liquid escapes the hood vents.

This demonstration of the reactions of lithium and sodium with water provides a visual reference for the property, some excitement, and breaks up the monotony of PowerPoint.  To provide more data, I often show a video of the reaction of potassium with water, such as this one.