[" 1.The electronic configuration of four elements are: "],[[" (1) "[Xe]6s^(1)," (2) "K times e]4f^(14)5d^(l)sigma^(2)," (c) Periodic "],[" (3) "[Ar]4s^(2)-4p^(5)," (4) "[Ar]3d^(7)4s^(2)," (d) A decreas "]]