How many protons, electrons and neutrons are there in the cation formed from an atom of magnesium that has a mass of 24?
(A) 12 protons, 12 electrons, 12 neutrons
(B) 12 protons, 10 electrons, 14 neutrons
(C) 12 protons, 10 electrons, 12 neutrons
(D) 14 protons, 12 electrons, 10 neutrons
(E) 10 protons, 12 electrons, 12 neutrons