Question

The aqueous solution containing which one of the following ions will be colourless? (Atomic number of $Sc=21,Fe=26,Ti=22,Mn=25$)

• A. $S{c}^{3+}$
• B. $F{e}^{2+}$
• C. $T{i}^{3+}$
• D. $M{n}^{2+}$

Answer 1

Answer: (A)

(a) ${}_{21}S{c}^{3+}=1s^2,2s^{2}2p^6,3s^{2}3p^6$
It is colourless due to absence of unpaired electrons in $d$ -subshell.
(b) $26F{e}^{2+}=1s^2,2s^{2}2p^6,3s^{2}3p^{6}3d^6$
It is colourless due to presence of four unpaired electrons in $d$ -subshell.
(c) ${}_{22}T{i}^{3+}=1s^2,2s^{2}2p^6,3s^{2}3p^{6}3d^1$
It is coloured due to presence of one unpaired electron in $d$ -subshell.
(d) ${}_{25}M{n}^{2+}=1s^2,2s^{2}2p^6,3s^{2}3p^{6}3d^5$
It is coloured due to $5$ unpaired electrons in d-subshell.