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Somewhere during the first few years of teaching chemistry, I decided to ask students to memorize the formulas for common ions. I don’t remember why I did this. It may have been because, as a new chemistry teacher, I didn’t know what else to ask students to do. Over the years, well, the decades, I continued to ask students to learn ion formulas because they worked much more quickly and with a better understanding if they weren’t stopping to look up every ion formula as they wrote equations for chemical reactions, and didn’t understand the difference between chloride, chlorite, and chlorate.
The ion study cards my students make are not your father’s flash cards. Nope. We use the cards to group ions by various similarities and note their differences. Their Ion Study Guide helps them navigate the patterns on the periodic table and in nomenclature that makes remembering names and formulas understandable.
Do students automatically memorize all 64 ion formulas after completing this study guide?
Nope. They do, however, have a baseline and a familiar resource to access when they need it.
Learn to understand:
My classes practice with this in class, using the first 2 pages of their Study Guide.
Then, they use the ion list, the ion study cards they made, a periodic table, and an Ion Summary Page to sort and organize their polyatomic ion cards by various categories. Which ions have the same elements? (ions containing Cl and O are a good place to start.) Put them in order by number of oxygen atoms and look at their names. Now try the same thing with ions containing S and O, then try N and O.
The Study Guide and Ion Summary Page walk students through several patterns that support understanding of formulas and nomenclature. If students will not be asked to memorize ion formulas, they have familiar references to use when writing chemical formulas. They have a basic understanding of formula names. And they can work more quickly than if they were simply looking up ion formulas with no concept of how the names were assigned and used. Surprisingly, students who complete this exercise often find they’ve accidentally “memorized” some of the more common ions.
A student who has memorized common monatomic and polyatomic ions will write ionic formulas and equations for chemical reactions much more expediently than a student who must stop and first look up the formula for every ion, then consult a reference on how to use the charges to correctly write the formulas.
Want to help your students master the use of ion formulas in writing compound formulas and equations? You can make a list of the ions you want students to know, have them make their own ion cards (we cut index cards in half) and give then a periodic table. You can make an organized Ion Summary Page for your students and make a Study Guide to guide them through learning the patterns on the periodic table and the names of ions. You can make them a list of study hints to help them use these resources.
Don’t have time to make your own versions? Grab my student-tested, tried-and-true, resources here. If you do, please leave a review! And, leave a comment letting me know how your students are doing with this adventure.