"Ionic Blocks" is a teaching tool designed to help middle school students visualize the concepts of ions, ionic compounds, and stoichiometry. It can also assist high school students in reviewing their subject mastery. Three dimensional blocks are used to represent cations and anions, with color indicating charge (positive or negative) and size representing charge magnitude. The students then assemble the "blocks" to form compounds of the correct stoichiometries. Individual students can also cut index cards of different colors to represent the ions, with card sizes proportional to charge magnitudes. When students physically construct compounds so that the lengths of the cation and anion blocks match, they quickly gain an intuitive understanding of charge balance in ionic compounds. The "blocks" also assist students in visualizing polyatomic ions as single units that are not broken down when electrolytes dissociate. The interactive activity fits into one class period, costs less than 3 cents per student, familiarizes students with the names, formulas, and charges of some common ions, and can introduce ionic compound names. (Contains 1 table.)