Mg^2+ Is this saying that the magnesium has gained two electrons? How do I determine the amount of protons and neutrons?

Question

I am reading chapter 2 of my textbook for the first time and it is talking about ions and how they either gain or lose an electron. What information am I supposed to take away or infere by the negative and positive numbers in the upper right hand of the symbol?

Answer 1

No. It is saying Mg has LOST 2 electrons. Recall that electrons are negative. If it had GAINED electrons it would be a negative ion. When you see a positive ion, the neutral atom has lost an electron(s), and if you see a negative ion, the neutral atom has gained an electron(s). Protons are given by the atomic number. Neutrons = atomic mass - atomic number.