Up to this point, we know how many oxygens are found within our trioxides and tetraoxides. Now it's time to take a look at how we determine their charges. We know that our trioxides are here within this group, and we know that they are called trioxides because they have 3 oxygens to them. To think about their charges, there's a pattern when we take a look at the periodic table. So starting with group 3a, we have minus 3. So this would be B2O3 minus or minus 3. Then we go minus 2, minus 1. So in minus 2, all those in group 4a would be XO2 minus, and then N3O3 would be minus 1. So here we determine the charges for the trioxides when they end with the name 'ate'. We'll get to that later on.
With the tetraoxides, the tetraoxide here, we're gonna start over again. So minus 3, minus 2, minus 1. So minus 3 here for P4O13 minus 3. We've determined that they have 4 oxygens because they're tetraoxides and this will be SO42-. Notice here we have another slot here for minus 1, which represents elements within this group 7a. We'll talk about them later on.
So at this point, we determine who our trioxides are and who our tetraoxides are, how many oxygens they have, and what their charges are. Now that we've taken a look at these different types of polyatomic ions, let's continue onward and take a look at additional ones.