NEET Chemistry NEET PYQ-The d-and f-Block Elements

  • question_answer
    Which of the following ions will: exhibit colour in aqueous solutions?               [AIPMT (S) 2010]

    A) \[L{{a}^{3+}}(Z=57)\]

    B) \[T{{i}^{3+}}(Z=22)\]

    C) \[L{{u}^{3+}}(Z=71)\]

    D) \[S{{c}^{3+}}(Z=21)\]

    Correct Answer: B

    Solution :

    [b] Key Idea Colour is obtained as a consequence of d-d (or f-f) transition, and for d-d (or f-f) transition, presence of unpaired electrons is the necessary condition.
    \[L{{a}^{3+}}(Z=57)=[Xe]4{{f}^{o}}5{{d}^{o}}6{{s}^{o}}\]
    (no unpaired electron)
    \[T{{i}^{3+}}(Z=22)=[Ar]3{{d}^{1}}4{{s}^{o}}\]
    (one unpaired electron)
    \[L{{u}^{3+}}(Z=71)=[Xe]4{{f}^{14}}5{{d}^{o}}6{{s}^{o}}\]
    (no unpaired electron)
    \[S{{c}^{3+}}(Z=21)=[Ar]3{{d}^{o}}4{{s}^{o}}\]
    (no unpaired electron)
    Hence, only \[T{{i}^{3+}}\]will exhibit colour in aqueous solution.


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