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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^+4The 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»

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.



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