So there are four protons within the nucleus, also four neutrons. And since our neutral atom has a charge of zero, that means if we have four protons, we must have four electrons. So two electrons are placed into the one s orbital, and two electrons are placed into the two s orbital. 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.