Therefore, neutral magnesium has 12 protons and 12 electrons. Magnesium ion | Mg+2 | CID 888 - structure, chemical names, physical and chemical properties, classification, patents, literature, biological activities, safety/hazards/toxicity information, supplier lists, and more. It's most common isotope is 24Mg, which has 24 - 12 = 12 neutrons. Total number of protons in the nucleus is called the atomic number of the atom and is given the symbol Z. Magnesium's, or Mg's, atomic number is 12. The nucleus is composed of protons and neutrons. 25. The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. COVID-19 is an emerging, rapidly evolving situation. Addition of number of protons and neutrons make up its mass number i.e. How many nuetrons are in … Magnesium has 13 neutrons,12 protons and same number of electrons. The chemical symbol for Magnesium is Mg.