When neptunium (Np) and plutonium (Pu) were discovered, the periodic table did not include the actinides, so these elements were placed in Groups 7B(7) and 8B(8). When americium(Am) and curium (Cm) were synthesized, they were placed in Groups 8B(9) and 8B(10). However, during chemical isolation procedures, Glenn Seaborg and his colleagues, who had synthesized these elements, could not find their compounds among other compounds of members of the same groups, which led Seaborg tosuggest they were part of a new inner transition series.(b) The highest fluorides of Np and Pu are hexafluorides, as is the highest fluoride of uranium. How does this chemical evidence support the placement of Np and Pu as inner transition elements rather than transition elements?