Well, it's been quite a while since I've done this, and i might be a little rusty so you might just want to double check, but chemistry in a way is kind of basically common sense in a way, so if your atom is neutral and you need to determine the protons, neutrons, and electrons, I would say that you need to calculate and find the one that would most likely, or is neutral. I don't know if this will be of much help, but as of right now it's the best that i can do.
