The constants of the Rydberg - Ritz equation

If the terms of the hydrogen spectrum to which certain quantum numbers have been assigned are compared with corresponding terms in the spectra of other elements, the latter will be found to be greater. While all writers agree that this is due to the presence of other orbital electrons, the structural reasons for this discrepancy are still a matter about which there is considerable difference of opinion. The present paper is an effort to consider this subject from a slightly new point of view. We may call such spectra hydrogen-like as arise from the radiation of the valence electron when it is alone in the outer shell. The alkali metals have such spectra normally and other elements give it in higher states of ionization. In all the cases to be considered, the valence electron moves about an atomic kernel, consisting of the nucleus and a number of electrons which move in orbits much smaller than those of the valence electron. The kernel is probably a structure geometrically similar to the atoms of the inert gases, but somewhat smaller, due to the contracting influence of the greater nuclear charge; and, unlike the inert gas atoms, the atomic kernel has a net positive electric charge. There was formerly some doubt about the total quantum numbers to be assigned to the valence orbit of the elements, but the correlations of X-ray and visible spectroscopy by Bohr and others have settled upon 3 as the total quantum number of the normal orbit in the sodium group, 4 in the potassium group, and so on.