MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

Inner transition elements are the f-block elements, which include the lanthanides (atomic numbers 58 to 71) and actinides (atomic numbers 90 to 103). Sometimes, Lanthanum (Z=57) and Actinium (Z=89) are also studied along with them due to their similar properties. Ho (Holmium, Z=67) and Lu (Lutetium, Z=71) belong to the lanthanide series. Ac (Actinium, Z=89) is the prototype of the actinide series. Rf (Rutherfordium, Z=104) is a transactinide element. It belongs to Group 4 and Period 7 of the periodic table, making it a d-block (transition) element, not an inner transition element. Answer: Rf