Chlorine Cl: 17 protons, 17 electrons, 7 Valence electrons, Nonmetal, Give 3, 14 new electrons, +1, Cl-
Magnesium Mg: 12 protons, 12 electrons, 3 Valence electrons, Metal, Give 2, 10 new electrons, 2-, Mg ^2+
Oxygen O: 8 protons, 8 electrons, 6 Valence electrons, Nonmetal, Give 6, 2 new electrons, -2, 0 ^2-
Nitrogen N: 7 protons, 7 electrons, 5 Valance electrons, Nonmetal, Give 4, 3 new electrons, -3, N ^3-
I really hope this helps :)
