The elements in which the extra electron enters ( n- 2 )f orbitals are called f-block elements. These elements are also called as inner transition elements because they form a transition series within the transition elements. The f-block elements are also known as rare earth elements. These are divided into two series.
i) The Lanthanide series (4f-block elements)
ii) The Actinide series (5f- block elements)
The position of f block elements in the periodic table, is explained above.