scienceflunk

I need some help on a few things I can't seem to find in either my book, nor my notes. I'm doing a phsyical science review paper, including definitions, and questions which is due tomorrow, and I've missed a bit of school already. So, some things I need help with are: 1.)At what temperature water has its greatest density? 2.)What part of the atom dictates its chemical properties? 3.)Given the atomic mass and atomic number, how do I calculate the number of protons, electrons and neutrons are in that element? 4.)How an atomic spectrum is made. 5.)How many valence electrons are in the main group of elements of the periodic table? 6.)What 7 diatomic elements are? 7.)How to tell an ionic compound from a covalent compound? 8.)What can be changed and what cannot be changed when balancing a chemical equation? --To be honest, I completely stink at science. I can't get the hang of it, so if anyone could help me out, it'd be GREAT! Please and thank you.