Maybe you already have a way to learn the polyatomic ions and their charges. I just memorized them in college and have used them so much that it isn't hard to remember them anymore. However, every year my students struggle learning the polyatomic ions. There just doesn't seem to be a pattern in the number of oxygen atoms and their charges. I was wrong. I found 2 methods of learning the polyatomic ions, one using a mnemonic and one using the periodic table. The mnemonic is:
The consonants in each stand for the number of oxygen atoms in the ion and the number of vowels stand for the negative charge on the ion. Really, try it. Nitrate has 3 oxygen atoms and a 1- charge. Nick has 3 consonants and 1 vowel. It works for every single one!
Lastly, the elements outlined in green (the "1") all have 3 oxygens and have a 1- charge.
Once you have learned the ions ending in "-ate," you can easily change the prefixes and sufixes when you change the number of oxygen atoms (-ate changes to -ite when an oxygen is removes and so forth).
This is a very simple way of learning the polyatomic ions. These methods will definitely help my students learn the ions.
If you want to learn even more about GooseChase, head over to the tutorial page I have on my Technology Toolkit site.