Use subscripts to indicate more than one ion of an element. Demonstrate, for example, how it takes two bromines to go with the one calcium. Quick check Divide students into 2 teams. Write a list of cations and anions on the board. Give each team one minute to write the correct chemical formula on an index card.
Teams get one point for each correct formula.
Name the compound and select a student at random to write the formula on the board. Each correct formula earns one correct point for that team. As with binary compounds, charges on the ions should cancel each other. Use parentheses for compounds with more than one of the same polyatomic ion. Do 1-15 in groups.