The number of elements in the lanthanoids of the periodic table is

The lanthanoids (formerly known as lanthanides) are a series of chemical elements in the periodic table that belong to the f-block. They are characterized by the progressive filling of the 4f electron subshell.

• An f-subshell consists of seven orbitals, and according to the Pauli Exclusion Principle, each orbital can hold two electrons. Therefore, the f-subshell can accommodate a maximum of 14 electrons.
• Consequently, the lanthanoid series consists of 14 elements, typically identified as those ranging from Cerium (atomic number Z=58) to Lutetium (Z=71).
• While the International Union of Pure and Applied Chemistry (IUPAC) technically includes Lanthanum (Z=57) in the group definition, standard textbooks (including NCERT) and competitive examinations define the f-block series itself as containing 14 elements based on orbital capacity.