You are balancing an ionic compound. let's call it: ab. ion a has a charge of +2 and ion b has a charge of -3. therefore, you determine that the ionic compound (ab) will have a ratio of 3 as for every 2 bs. how would you modify ab in order to show that they have this 3-to-2 ratio? a^3b^2 3a2b a3b2

A₃B₂

Explanation:

In a chemical formula the subscripts indicate the number of atoms or ions of each element, so in the formula A₃B₂, the subscript 3 indicates that the unit formula has three ions of element A, and the subscript 2 indicates 2 ions of the element B. Hence, the ratio A to B is 3 : 2.

You check the correctness of the unit formula by adding the total charges knowing that the final net charge of a neutral compound is zero. This table shows the balance of the charges for the compound A₃B₂:

Ion      Charge         Number of ions                      Total charge

          (each ion)      (subscript in the formula)      (# ions × charge per ion)

A              +2                      3                                     +2 × 3 = +6

B               -3                      2                                     -3 × 2 = - 6

                                                     Net charge:        +6 - 6 = 0

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