Question

Which of the following lanthanide ions do not exhibit color?

(a) Lu^+3 and Ln^+3

(b) Lu^+2 and Ln^+2

(c) Ce^+3 and Ce^+3

(d) Pr^+4 and Ce^+4

The question was posed to me during an internship interview.

The origin of the question is D and F-Block Elements topic in section D and F-Block Elements of Chemistry – Class 12

Answer 1

Correct answer is (a) Lu^+3 and Ln^+3

For explanation: Many trivalent lanthanide ions are colored both in the solid state and in aqueous state due to f-f electronic transition. Lu^+3 and Ln^+3 don’t exhibit color due to absence of unpaired electrons. All lanthanide ions except La^+3, Ce^+3 and Lu^+3 are paramagnetic due to presence of unpaired electrons.