Up to this point, we just examined polyatomic ions that possess a negative charge. Now it's time to look at the positively charged ones. We're going to say most polyatomic ions are negatively charged except for NH4+ ion and Hg22+ ion.
We're going to say NH4+ is called the ammonium ammonium ion, and it's going to be the only major polyatomic ion that you're going to need to know that has a +1 charge. Then we're going to say we have Hg22+ and know that little 2 is not a typo. What this is, It's two individual Hg1 mercury ions. They combine together.
So now there's two of them together and their combined charge comes out to two plus because each one possesses a +1 charge. We're going to say this is called Mercury One ion. Yes, I know it might be a little bit confusing because the charge is 2 plus, but realize that that two plus comes from the fact that each Mercury is +1.
All right, So again, a vast majority of the polyatomic ions you're going to encounter possess a negative charge. These two possess positive charges.