Which alkaline earth metal has 3 occupied energy levels?

The alkaline metal with three rings would be magnesium(Mg). It has an atomic number of 12 and Atomic Mass if rounded is 24. Protons and eletrons are 12 (Electrons are always the same number as protons and the number of protons is the same as the atomic number)and Neutrons( found out by subtracting the atomic mass from the number of protons) is 12.

It would have 3 rings because there are 12 electrons. So, 2 electrons can be in the first orbit, 8 in the second, and 8 in the third. Basically you must fill up the first and second orbit and then in the third you have only 2.