Question

What are inner transition elements? Decide which of the following atomic numbers are the atomic numbers of the inner transition elements : $29,59,74,95,102,104$.

Answer 1

Inner transition metals are those elements in which the last electron enters the f-orbital. The elements in which the $4f$ and the $5f$ orbitals are progressively filled are called f-block elements. These includes lanthanoids ($Z=58-71$) and actinoids ($Z=90-103$).

Elements with atomic numbers 59, 95 and 102 are inner transition elements.