Much like the classic Sudoku, this puzzle makes students apply their knowledge of cation charges. Looking at the provided compounds, students must figure out how to get a +1, +2, and +3 in every row and column of each 3x3 block. Additionally, no cation of the same element can exist in the same column or row across the 9x9 board. A board is provided with one row and column filled in (to show students how to do it correctly). Then, another sheet is provided for the instructor to cut into cards for the students to arrange on their desks before committing their final answers in writing on their board. Uncut, this other sheet also serves as an answer key for the instructor.