Question

Which one of the following ionic species will impart colour to an aqueous solution ?

• A. $T{i}^{4+}$
• B. $C{u}^{+}$
• C. $Z{n}^{2+}$
• D. $C{r}^{3+}$

Answer 1

Answer: (D)

$C{r}^{3+}=1s^2,2s^{2}2p^6,3s^{2}3p^{6}3d^3$ (coloured)
$(C{r}^{3+}$ contains 3 unpaired $e^{-}$, so it gives colour)
$Z{n}^{2+}=1s^2,2s^{2}2p^6,3s^{2}3p^{6}3d^{10}$ (colourless)
$C{u}^{+}=1s^2,2s^{2}2p^6,3s^{2}3p^{6}3d^{10}$ (colourless)
$T{i}^{4+}=1s^2,2s^{2}2p^6,3s^{2}3p^6$ (colourless)
(Colour is produced due to presence of unpaired electrons.)