Considering the stringent structural definition of the inner transition series (where electrons prog — d and f Block Elements Chemistry Question

💡 Solution & Explanation

The Lanthanoid series involves the progressive filling of the deeply buried $4f$ subshell. Because any $f$ -subshell is composed of exactly $7$ spatial orbitals, and the Pauli Exclusion Principle dictates that each orbital can hold a maximum of $2$ electrons, the entire $4f$ subshell can accommodate an absolute maximum of $14$ electrons. Consequently, the Lanthanoid series rigidly consists of exactly $14$ elements (from Cerium, $Z=58$, to Lutetium, $Z=71$).