• # question_answer The aqueous solution containing which one of the following ions will be colourless? (Atomic number: ($\operatorname{Sc} = 21, Fe = 26$, $\operatorname{Ti} = 22, Mn = 25)$ A) $S{{c}^{3+}}$          B)        $F{{e}^{2+}}$ C) $T{{i}^{3+}}$           D)        $M{{n}^{2+}}$

${{\operatorname{Sc}}^{3+}}\to \,\,3{{d}^{6}}\,4{{s}^{0}}$ ${{\operatorname{Fe}}^{2+}}\to 3{{d}^{6}}\,4{{s}^{0}}$ ${{\operatorname{Ti}}^{3+}}\to \,3{{d}^{1}}\,4{{s}^{0}}$ $M{{n}^{2+}}\to 3{{d}^{5}}\,4{{s}^{0}}$   In $S{{c}^{3+}}$ there is/are no unpaired electrons. So the aqueous solution of $S{{c}^{3+}}$ will be colourless.