In chemistry how does one determine the following in isotopes and elements?

I am specifically looking into learning how for any element on the periodic table with an isotope one person may determine the following: Mass number? Number of electrons? nuclear charge of +15? has no neutrons, has no electrons, has a number of neutrons twice that of electrons, has a number of nuetrons twice that of protons? has ten electrons? has an equal number of protons, neutrons, and electrons? has a number of electrons equal to that of neutrons, but different than that of protons? has a number of neutrons (other than zero) which is less than the number of protons?

This is a homework question. I do not want you to answer the question for me, because then I won't learn how to do it myself which is why I am not specifiying the isotopes or elements directly involved. I want something that can be used and applied to all of the above problems. I am a visual learner, and reading it out of a textbook is just not helping at all.