So, if we took the case of nitrogen, if we add an electron to nitrogen and go to n minus, we find that the change in energy is 7 kilojoules per mole.

In their 1916 papers, both G. N. Lewis and W. Kossel pointed to the electron configurations of these elements as especially stable.

And, in fact, it can't even reach n, because then we would have no potential energy at all in our electron, which is not correct.