Question

Which of the following metal ions is colourless in water?

• A. $V^{2+}$
• B. $C{r}^{3+}$
• C. $F{e}^{2+}$
• D. $S{c}^{3+}$

Answer 1

The correct option is D $S{c}^{3+}$

The electronic configuration of
$V^{2+}=\left[Ar\right]3d^1$
$C{r}^{3+}=\left[Ar\right]3d^3$
$F{e}^{2+}=\left[Ar\right]3d^6$
$S{c}^{3+}=\left[Ar\right]3d^0$
Since in $S{c}^{3+}$ there is no $d-$ electrons, thus $d-d$ transition is not possible here and it will not show any colour.