At element 121, the superactinide series is expected to begin, when the 8s electrons and the filling 8p 1/2, 7d 3/2, 6f 5/2, and 5g 7/2 subshells determine the chemistry of these elements. Complete and accurate calculations are not available for elements beyond 123 because of the extreme complexity of the situation: the 5g, 6f, and 7d orbitals should have about the same energy level, and in the region of element 160 the 9s, 8p 3/2, and 9p 1/2 orbitals should also be about equal in energy. This will cause the electron shells to mix so that the block concept no longer applies very well, and will also result in novel chemical properties that will make positioning these elements in a periodic table very difficult.