Inner transition metal
periodic table block; in the center-left of a 32-column periodic table but in the footnoted appendage of 18-column tables.
Inner transition metals (ITM) are chemical elements on the periodic table. They are normally shown in two rows below all the other elements. They include elements 57-71, or lanthanides, and 89-103, or actinides. The lanthanides are very similar, and the actinides are all radioactive.
ITMs have three incomplete outermost nucleus shells and are all metals. In some cases they are quite malleable and ductile. Many lanthanides such as Lutetium are used in the lighting industry. Actinides do not occur in nature (except for thorium and uranium), and are highly unstable.
The last electrons enter into the f orbitals of these elements, so they belong to the F-block. The general electron configuration is (n-2)f^0-14(n-1)d^0-2np^6ns^2 where n= 6-7.