Question

Predict which of the following will be coloured in aqueous solution?

• A. $S{c}^{3+}$
• B. $C{r}^{3+}$
• C. $V^{3+}$
• D. Both (b) and (c)

Answer 1

The correct option is D Both (b) and (c)

Only those ions will form colored complexes with $H_{2}O$ which have incompletely filled $d-$orbitals. The ions with either empty or filled $d-$orbitals are colourless.
Out of $S{c}^{3+}\left(3d^0\right),C{r}^{3+}\left(3d^3\right)\text{and}{V}^{3+}\left(3d^2\right)$, $C{r}^{3+}\text{and}{V}^{3+}$ contain unpaired electrons while $S{c}^{3+}$ contains empty $d-$orbitals hence, $C{r}^{3+}\text{and}{V}^{3+}$ will show color in aqueous solution whereas $S{c}^{3+}$ will be colorless in aqueous solution.