Decoding the Periodic Table

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Objective

SWBAT use the information present in a cell of the periodic table to determine the structure of the element's atoms.

Big Idea

Prior knowledge about atomic structure is connected to the layout of the periodic table.

Background

This lesson is designed after very pointed feedback from my students.  After the first unit was primarily guided inquiry, students indicated being uncomfortable with that process.  At this point, I went back to student entry surveys and approximately 30% of students indicated a preference for teacher lecture and note taking.  While I am not willing to abandon inquiry-based instruction, I am aware that I need to structure and introduce it differently to be successful with my students this year.

This lesson continues to build on HS-PS1-1.  We are learning how to use the information presented in the periodic table to understand what it tells us about individual elements.  Yesterday’s lesson focused on the overall structure of the periodic table, today we drill down to how to describe the periodic table, and what each cell represents.  By doing this, we are setting the parameters for the periodic table as a primary model, addressing Science and Engineering Practice 2: Developing and Using Models.

Advanced students may begin to engage the Patterns Cross Cutting Concept, where charts and tables allow for distinguishing patterns in data.  Although this is not the emphasis of the lesson, many students pick up on the patterns of atomic mass and atomic number present in the basic periodic law.

Bellringer

5 minutes

When students enter the room, the question “What are the three types of elements?” is either written on the board or projected on the screen.  Students answer this question in their binders while I take attendance.  This is a review of the previous day’s lesson color coding the periodic table and using the colors to differentiate between metals, non-metals and metalloids.  While students are answering the question, I return their colored periodic tables, which helps to un-stick students who don’t remember.

I then ask for whole class responses, getting the three type of elements, each one from a different table.  I ask students to look at their colored periodic tables.  I ask how they would know where the noble gases are.  Many students have no idea, but those who made good keys for their tables are able to respond.  I then stress the importance of having a good key on their model so they can use it as we go.

I ask them to keep out their periodic tables, but to turn to a blank page to take notes today.

Whole Class Instruction

25 minutes

While students are setting up their paper for notes, I explain to them that I have heard their feedback that we should do more notes.  I then explain that taking notes is a skill, not just copying what is on screen.  To this end, I point out some things to students as we go through our Using the Periodic Table PowerPoint.

  • I refer back to labeling the periods on the left side of their color-coded table, and encourage students to draw a sideways arrow in their notes.
  • When discussing groups I remind them of finding the group number on top of each column, and encourage students to draw an up-and-down arrow in their notes.
  • When discussing the location of each type of element, I ask which one is the exception to the rule of metals to the left and non-metals to the right.  I point out that exceptions to rules are important to have in their notes, so Hydrogen as a non-metal on the left side of the periodic table is crucial to record.
  • Many students do not want to write down and label examples, so when discussing the single cell, I have them first copy down the Carbon sample, and then we label each part rather than just take the notes in outline form.
  • For the whole class practice, students will begin writing down the whole question.  I have them stop, read the question, copy the example and then write down the answer to the question.

While students are working on the example, I pass out the paper for the individual practice.

Individual Practice

15 minutes

I ask students to put their names on the Periodic Table and Particles practice sheet.  I then explain how the top of the page summarizes what we learned previously about sub-atomic particles and more recently about using the periodic table today.

We take the Iodine example from our notes, and apply it to the first row so students have an exemplar to refer to.  Here is an example how.

After putting the Iodine example onto the page, I review the instructions, 15 elements that represent every period of the periodic table, and no more than one element per group of the periodic table.  At this point, I let them work independently and walk the room to answer questions.

Students tend to struggle with the "most common version" (isotope) cell, either from forgetting how to do it, or incorrectly rounding the numbers.  The other common mistake is in calculating neutrons.  Although students now know the mass of protons and neutrons is counted as one, their number sense fails them in how to calculate the neutrons from the atomic mass.  When students are clearly struggling, I take a highlighter and show the math like this.

 

Below is a sample of student work from this year.

 I give students a 3 and 1 minute warning before heading into our closing activity.

 

Closure

5 minutes

For the closing activity, I ask students to flip their paper over, and write two facts they learned today about how to use an individual cell on the periodic table.  I then have them turn in their papers as they exit the room.

The most common responses are:

  1. The symbol has to be a capital and lower case letter
  2. The atomic number is the number of protons and electrons
  3. The atomic mass can be rounded and used to find neutrons

The troublesome one here is number 2.  Many students forget the qualifier that this is only true for NEUTRAL atoms.  It is something that I will touch on again the following day if it is a lot of the class, and I insert the word "neutral" in their feedback.