Suppose that X represents an arbitrary cation and that Y represents an anionic species. Using the charges indicated in the super
script of X and Y, fill in the remaining blanks below by writing the appropriate subscript for each X and Y to balance the net charge on the ionic XaYb compound formed (where a and b represent positive, whole numbers of X and Y, respectively). Y- Y2- Y3-
X+
X2+ XY2
X3+
In this case, when having the cationic and anionic species with the specified charges, in order to abide by the net charge rule, we need to exchange the charges in the form of subscripts and without the sign, just as shown below: