-quanta orbits. Only when the development of this group has been completed may we expect to find once more a corresponding change in the properties of the elements with increasing atomic number such as we find in the preceding periods. The properties of the elements in the latter part of the fourth period show immediately that the group, when completed, will possess
electrons. Thus in krypton, for example, we may expect besides the groups of
,
and
-quanta orbits a markedly symmetrical configuration of