Question

Total number of inner transition elements are:

Answer 1

To answer this question, you should recall the formation of the periodic table. The inner transition elements are also known as f-block elements. They contain a partially or fully filled f-orbital.

Complete step by step answer:
Inner transition elements refer to the elements constituting the f-block are those in which 4f and 5f orbitals are progressively filled. These elements are formal members of group 3 but are shown separately as f-block of the periodic table. The elements of f-block are also called inner transition elements.
There are two series of inner transition elements which are known as lanthanide or 4f series and actinoids or 5f series. The inner transition elements such as Uranium, Thorium and Protactinium are used as sources of nuclear energy.
The electronic configuration of the inner transition elements is $4{f^{1 - 14}}5{p^6}5{d^{0 - 1}}6{s^2}\;$ for the lanthanides beginning at cerium $\left( {Z = 57} \right)$ and ending at lutetium $\left( {Z = 71} \right)$ and $5{f^{1 - 14}}6{s^2}6{p^6}6{d^{0 - 1}}7{s^2}\;$ for the actinides beginning with thorium $\left( {Z = 90} \right)$ and ending with lawrencium $\left( {Z = 103} \right)$
There are 28 inner transition elements. They include elements from atomic number 57−71 (14 lanthanides) and atomic numbers 89−103(14 actinides).

Note:
There are 4 blocks in the periodic table: s-block, p-block, d-block and f-block. All of the s-block elements are metals. Usually, they are shiny, silvery, good conductors of heat and electricity, and lose their valence electrons easily. The p-block due to its ability to accommodate a large number of electrons has the biggest variety of elements and is the only block that contains three types of elements: metals, nonmetals and metalloids. d-block elements have properties that are between s-block elements and p-block elements properties. It consists of transition metals. The f-block elements are mostly radioactive.