outside a ring of
electrons already bound, must be expected to take place more easily than the confluence of two similar rings rotating round a nucleus of charge
; for the stability of the rings for a displacement perpendicular to their plane will (see [§2]) be smaller in the first than in the latter case. This tendency for stability to decrease for displacements perpendicular to the plane of the ring will be especially marked for the outer rings of electrons of a neutral atom. In the latter case we must expect the confluence of rings to be greatly facilitated, and in certain cases it may even happen that the number of electrons in the outer ring may be greater than in the next, and that the outer ring may show deviations from the assumption of
,
,