In which of the following are the 5f orbitals progressively filled?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Actinoids
NCERT (2026-27 edition):
The d- and f-Block Elements – “The f-block consists of elements in which 4 f and 5 f orbitals are progressively filled. … The two series of the inner transition metals; 4f (Ce to Lu) and 5f (Th to Lr) are known as lanthanoids and actinoids respectively.”