In Kossel's paper, he writes: “This leads to the conclusion that the electrons, which are added further, should be put into concentric rings or shells, on each of which ... only a certain number of electrons—namely, eight in our case—should be arranged.
In Kossel's paper, he argues that electrons added further should be placed in concentric rings or shells, each of which can accommodate a limited number of electrons—namely, eight in our case.