question_answer 70)

        Generally transition elements and their salts are coloured due to the presence of unpaired electrons in metal ions. Which of the following compounds are coloured? (a)                          (b)      (c)                               (d)

Answer:

                      (a, b)  is coloured due to the charge transfer and not because of the presence of unpaired electrons. Similarly, oxidation state of Ce in  is +4 with  electronic configuration. It is also coloured (yellow) due to charge transfer and not due to f ? f transition.