Question

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

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

Answer 1

Answer: (D)

$Lu^{3+} = 4f^{14}$ Colourless
$Sc^{3+} = 3d^0$ Colourless
$La^{3+} = 4f^0$ Colourless
$Ti^{3+} = 3d^1$ Coloured (purple)
Transition metal ions and inner transition metal ions having $d^1$ to $d^9$ configuration and $f^1$ to $f^{13}$ configuration are coloured due to $d-d$ transition and $ f - f$ transition respectively. Ions having $d^0$ and $d^{10}$ or $f^0$ and $f^{14}$ configuration are colourless.