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: Locate each element
Ac: 89, Ho: 67, Lu: 71, Rf: 104.

Step 2: Series boundaries
Lanthanoids occupy 57 to 71 and actinoids occupy 89 to 103. Ho, Lu and Ac fall inside these ranges.

Step 3: Outside
104 is outside both ranges. Rf has the configuration $[\text{Rn}]5f^{14}6d^{2}7s^{2}$ with the f subshell already full and the new electrons going into 6d.

Step 4: Answer
Rf, option (A).

Final Answer:
Rf lies beyond the actinoid series. This is option (A). \[ \boxed{\text{(A) }\text{Rf}} \]