Q. Lanthanoid ions with $4f^7$ configuration are : (A) Eu²⁺ (B) Gd³⁺ (C) Eu³⁺ (D) Tb³⁺ (E) Sm²⁺ Choose the correct answer from the options given below :
A) (A) and (D) only
B) (B) and (C) only
C) (A) and (B) only
D) (B) and (E) only
Explanation
[Solution by Dr. Abubacker] Eu²⁺ is $4f^7$, Gd³⁺ is $4f^7$, Eu³⁺ is $4f^6$, Tb³⁺ is $4f^8$ and Sm²⁺ is $4f^6$. Only (A) and (B) are $4f^7$. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.