Now, notice that Beryllium is one guy over to the right on their periodic table. That means it has four protons and four electrons, while lithium has three protons and three electrons. Let's compare the atomic structure. So, the atomic structure of lithium is the following. Two of its electrons are found in the innermost shell, the one s shell. And one electron, because it only has three electrons, is found in the outermost two s shell.