Q. Which of the following ions will exhibit colour in aqueous solutions?
A) Sc³⁺ (Z = 21)
B) La³⁺ (Z = 57)
C) Ti³⁺ (Z = 22)
D) Lu³⁺ (Z = 71)
Explanation
[Solution from source] Ti³⁺ is 3d¹ with one unpaired electron, so a d-d transition gives colour (violet). Sc³⁺ (3d⁰), La³⁺ (4f⁰) and Lu³⁺ (4f¹⁴) have no unpaired d/f electrons and are colourless. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.