How do you find out the charge of a compound/ion when a question just says "Calcium ion"? Do I need more info on it, am I missing something? I'll give a few examples: Sulfite ion sulfur dioxide sulfur trioxide I need to know the number that goes in front of the charges. Please don't just give me an answer for these 3, if you could also explain how you got the answer it would greatly be appreciated. Thanx.