Question: how many protons and electrons are present in the mg2+ ion?
Answer: The latter is more energy efficient, thus the Magnesium atom decides to lose two electrons. Now since the nuclei only has 10 electrons in comparison to 12 protons, and since an electron = -1 charge while a proton = +1 charge, the net charge = +12–10=+2. Thus Mg2+ only has 10 electrons.