Question

Which of the following ions will exhibit colour in aqueous solutions?

• A. $Sc^{3 +}\left(\right.Z=21\left.\right)$
• B. $La^{3 +}\left(\right.Z=57\left.\right)$
• C. $Ti^{3 +}\left(\right.Z=22\left.\right)$
• D. $Lu^{3 +}\left(\right.Z=71\left.\right)$

Answer 1

Answer: (C)

Here only $Ti^{3 +}$ has one unpaired electron so it gives colour in aqueous solution due to d-d $e^{-}$ transition. Rest ions are colourless as they don’t any un-paired electron so no d-d electronic transition.