Magneziul are 12 protoni,12 neutroni, 12 electroni,formand 1 atom. Calciul are 20 protoni,20 neutroni, 20 electroni,formand 1 atom. Strontiul are 38 protoni, 38 neutroni,38 electroni,formand 1 atom. Bariul are 56 protoni,56 neutroni,56 electroni,formand 1 atom.