First, I want to understand something. Everything I look at suggests that the ionization energy of an atom or ion is suppose to be the energy needed to remove the 'outermost electron'- which I find troubling conceptually, since they also refer to this as the one with the highest energy. Wouldn't the hardest electron to remove be the groundstate? Why am I told not to think of this electron as a groundstate and certainly not as an n=1 electron, as was the case in Bohr's original theory? Second, does anyone know how the ionization energy of the atoms and ions are experimentally determined? In a laboratory? Finally, how does QT estimate or calculate the ionization energy of Helium I or other systems? In retrospect, Bohr was only able to calculate the ionization energy of Helium II... If QT is better, how does it calculate this value- or do these measurements remain experimentally determined? Anyone have any idea- in whole or in part?