When you have a non-metal, it ends in -ide when you place it into a chemical bond. These are all diatomic molecules (apart from phosphorus) and as such you take the element name, remove the suffix, and add -ide. When converting back, look at the electronegativity levels on your periodic table in the upper right corner of each element. (if you don't have them, google "nyc regents chemistry reference table" and go to page 6 of the first result.) The first charge in that spot is what the charge will be.
