quite similar. . . .
. . . La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Figure .
Variation of atomic radii of lanthanoids XII U4-D-Block-Jerald XII U4-D-Block-Jerald - - - - The elements of the second and third transition series resemble each other more closely than the elements of the first and second transition series. For example Series Element Atomic radius 3d Series Ti pm 4d Series Zr pm 5d Series Hf pm Actinoids: The fourteen elements following actinium ,i.e., from thorium (Th) to lawrentium (Lr) are called actinoids. Unlike the lanthanoids, all the actinoids are radioactive and most of them have short half lives. Only thorium and uranium(U) occur in significant amount in nature and a trace amounts of Plutonium(Pu) is also found in Uranium ores.Neptunium(Np) and successive heavier elements are produced synthetically by the artificial transformation of naturally occuring elements by nuclear reactions.
Similar to lanthanoids, they are placed at the bottom of the periodic table. Electronic configuration: The electronic configuration of actinoids is not definite. The general valence shell electronic configuration of 5f elements is represented as [Rn]5f - 6d - 7s . The following table show the electronic configuration of actinoids.
Table : electronic configuration of actinoids Name of the element Atomic number Symbol Electronic configuration Actinium Ac [Rn] 5f d s Thorium Th [Rn] 5f d s Protactinium Pa [Rn] 5f d s Uranium U [Rn] 5f d s Neptunium Np [Rn] 5f d s Plutonium Pu [Rn] 5f d s Americium Am [Rn] 5f d s Curium Cm [Rn] 5f d s Berkelium Bk [Rn] 5f d s Californium Cf [Rn] 5f d s XII U4-D-Block-Jerald XII U4-D-Block-Jerald - - - - Name