So what this basically means is that in order to remove an electron from the outermost shell of my Beryllium atom, I must input energy. I must do work on my atom to take that electron away. So if I input enough energy, I will be able to pluck this outermost electron away to form the following Beryllium atom. Now, the number of protons is the same. Before, we have four protons, and now we have four protons. So that means that we still have a Beryllium atom.