Polyatomic ions represent tightly bound groups made of different elements that possess an overall charge. That charge can be either positive or negative. For now, we're going to focus only on the negatively charged ones, so we're going to take a look at our polyatomic oxyanions. These are the negatively charged polyatomic ions that end with oxygen. And when it comes to these polyatomic oxyanions, we can describe them as either being trioxides or tetraxides.
Let's focus on the trioxides first. Let's focus on the fact that it has the letter T. If we look at this portion of the periodic table, we're going to say that these 4 in blue represent possible trioxides and they also form the letter T. Now the trioxides themselves we say when their name ends with "ate," they possess 3 oxygens. So again, use this to help you reinforce this. Trioxides with T. When they end with "ate," they have 3 oxygens. They form the letter T on the periodic table, so they all have three oxygen. So that's BO3, CO3, NO3, and SiO3.
Then we have our tetroxides. Tetra, some of you may know what that stands for. Tetra oxides. When their name ends with "ate," they possess 4 oxygens because tetra stands for four, and those are represented by phosphorus and sulfur. So they would have 4 oxygens, so PO4 and SO4.
All right, we've said oxyanions, so we talked about a negative charge, but we don't see it quite yet. Click on to the next video and let's take a look when we start incorporating charges with these trioxides and tetroxides.