I created these practice sheets to help my students understand and practice writing formulas for ionic compounds. This concept is relatively simple, but the application of this skill and plenty of practice are what help it sink in. The first sheet contains a basic overview of the rules for writing formulas and a page and a half of practice problems including two written as they might see on a standardized test and two challenge problems that test their understanding of the underlying concept. The second sheet takes the skill a step further, and it reviews how to predict the charges of ions, reviews the criss-cross method, then forces students to put these skills together to predict the charges before they can write the formula.