Question

Which of the following ion will give colourless aqueous solution ?

• A. $N{i}^{2+}$
• B. $S{c}^{3+}$
• C. $C{u}^{2+}$
• D. $M{n}^{3+}$

Answer 1

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

Solution:- (B) ${Sc}^{+3}$

Only the ions that have electrons in $d$-orbital and in which $d-d$ transition is possible will be coloured.

Electronic configuration of ${Sc}^{+3}\left(\text{At. no. = 21}\right)-1s^{2}2s^{2}2p^{6}3s^{2}3p^6$

Since it do not contains electrons in $d$-orbital and hence will not undergo $d-d$ transition and do not show colour.