A group of 15 ra-dioactive elements whose electronic configu-rations display filling of the 5f level. As withthe lanthanoids,the first member,actinium,has no f electrons (Ac[Rn]6d17s2) but othermembers also show deviations from thesmooth trend of f-electr......（本文共 904 字）     [閱讀本文] >>