Question

Which from following is NOT an inner transition element ?

• A. \(\text{Rf}\)
• B. \(\text{Ac}\)
• C. \(\text{Lu}\)
• D. \(\text{Ho}\)

Hint:

Inner transition elements are the lanthanoids (4f) and actinoids (5f); Rf is a 6d element.

Answer 1

The Correct Option is A

Step 1: Understand the concept
Inner transition elements are the f-block elements: the lanthanoids (Ce to Lu, 4f series, with La as the parent) and the actinoids (Th to Lr, 5f series, with Ac as the parent).

Step 2: Check Ac, Lu and Ho
Ac (Z = 89) heads the actinoid series. Lu (Z = 71) is the last member of the lanthanoid series. Ho (Z = 67) is a lanthanoid. All three belong to the f-block series.

Step 3: Check Rf
Rutherfordium (Z = 104) comes after the actinoids. It is a 6d element placed in group 4 below Hf, so it is a d-block (transition) element.

Step 4: Conclusion
Rf is the one that is not an inner transition element.

Final Answer:
Rf is a 6d block element, not an f-block element. This is option (A). \[ \boxed{\text{(A) }\text{Rf}} \]