Now, what this principle states is the following. Whenever an atom adds a new proton to create a new atom element, it must also add another electron to neutralize that extra charge that comes from that extra proton. So the problem is the following whenever we add a proton, we know exactly where our proton goes. That proton goes into the nucleus along with all the other protons. What about our electrons? We have options as to where to place those electrons.