AIIMS 2014 Chemistry Periodic Table MCQ Question

The correct answer is D) Terbium (Z = 65) because it is not an actinoid; instead, it is a lanthanide, which is part of the f-block elements in the periodic table. Actinoids are the series of 15 elements from actinium (Z = 89) to lawrencium (Z = 103), characterized by their filling of the 5f orbitals, whereas terbium fills the 4f orbitals.