Adding Inquiry to Atomic Theory

Having some experience in using and creating inquiry activities, I am getting questions from teachers looking for ways to add inquiry to their curriculum. My first tip is to take baby steps. I will continue to blog about ideas to help outline some of those steps. First, I am sharing some inquiry ideas from the last unit I taught in my high school general chemistry course along with providing some ideas for using the resources provided with a subscription to ChemEdX.

My students have already been introduced to the history of atomic theory before they see it in my high school’s general chemistry course. I almost wish they hadn’t been. If you teach high school chemistry, you probably know that middle school texts often encourage a misconception that when we write electron configurations or draw atomic models, every energy level must be completely filled with electrons before we may add electrons to the next level. When my daughter studied atomic theory in her eighth grade science course, she was instructed to create large models of several elements. She showed me a model of copper she had made. It had two electrons in the first energy level, eight in the second, eighteen in the third and then one in the fourth level. I pointed out her error and then taught her about sublevels and the fact that we don’t generally see more than eight valence electrons. She understood and adjusted her models. Then, she came home with a poor homework grade along with a poor test grade. Her teacher followed the letter of the text and refused to adjust his thinking because he relied on the text for his information. I couldn’t make him understand that Amber’s models were actually correct. For this same reason, many of my students try to argue over the idea of filling sublevel 4s before adding electrons to 3d. It takes some convincing to get the students to trust me that in the course of a week, they will have enough information to understand why we can do that.

I start my discussion of atomic theory by assigning individual postulates of Dalton’s theory to groups of students. They read about the history of atomic theory in their texts, discuss amongst their groups and then the groups report if their assigned postulate is valid, invalid or partially valid along with explanations to support their ideas. We discuss the modern electron cloud model, but like most teachers I know, we use the Bohr model in our lessons.

Like many teachers, we review Rutherford’s model and the questions surrounding it. We then see how Bohr used flame tests to support the idea of energy levels. I give my students a chance to perform some flame tests on their own, but I show them more by directing them to Chemistry Comes Alive Volume 7 (subscriber only content, subscription required for access).

We also look at tubes of gas lit up by a power source using a hand held spectroscope. I have found it helpful to direct my students to ChemPages Laboratory Resources that review the background of these tools. In our discussions about “why” the flame tests led to the idea of energy levels, I often refer to the Wintergreen lifesaver demo. Add some inquiry by requiring students to come up with an explanation relating to atomic theory after biting into the Lifesaver. It is worth the effort to find a dark place to take your students to see this for themselves. I provide every student with a lifesaver and take them to the auditorium. I stand with the door ajar to provide light for students to prepare. They face a partner and then I close the door. I wait a few moments for our eyes to adjust and then I tell them to bite down with their mouths open or use a pair of pliers (the latter method requires finding all those pliers and it is much messier).

During this unit, we also use spectrophotometers to expand on the idea of light waves and perform an inquiry activity testing food dyes (to be linked here soon). I direct students again to the ChemPages Laboratory Resources that review the background of the Spectronic 20^TM. Using ChemPages has helped me with preparing my students to use both the hand held spectroscope and the Spec20 with less effort than I had devoted before using that resource.

As I alluded to in the first paragraph, I teach my general chemistry students the order of filling the sublevels by providing a list of the order. However, once my students are somewhat proficient at writing the configurations, I incorporate another inquiry activity by providing them with a blank periodic table and instructing them to write the noble gas shortcut configuration for every element in the boxes on the table. I then provide a series of questions to help them discover the patterns that can be seen. I do continue to provide the list of the order of filling the sublevels during the general chemistry course, however I point out to those considering enrolling in Advance Placement Chemistry that they should be able to write the configuration without that list and most can before we are done with the unit. Depending on the level of your students, this may be the perfect time to take away the list of the order. This activity also lends itself to a discussion introducing our next topic, the Periodic Table.

I am looking forward to discussing my unit covering the Periodic Table. I used to consider it one of the dullest topics within my course, but I also thought it deserved more. Considering that the table sums up everything else that I teach, I decided that I had to make learning the material more exciting.