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NCERT Class XII Chemistry
Chapter - The d- and f-Block Elements
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Question : 18 of 49
Marks: +1, -0
Predict which of the following will be coloured in aqueous solution?
Ti3+,V3+,Cu+,Sc3+,Mn2+,Fe3+\mathrm{Ti}^{3+}, \mathrm{V}^{3+}, \mathrm{Cu}^{+}, \mathrm{Sc}^{3+}, \mathrm{Mn}^{2+}, \mathrm{Fe}^{3+} and Co2+\mathrm{Co}^{2+}. Give reasons for each.
Solution:  
The configuration of the given metal ions can be given as
Ti3+–  3d14s0  \mathrm{Ti}^{3+} \text{--}\; 3d^{1}4s^{0}\; 1 unpaired electron
V3+–  3d24s0  \mathrm{V}^{3+} \text{--}\; 3d^{2}4s^{0}\; 2 unpaired electrons
Cu+–  3d104s0  \mathrm{Cu}^{+} \text{--} \; 3d^{10}4s^{0}\; No unpaired electron
Sc3+–  3d04s0  \mathrm{Sc}^{3+} \text{--}\; 3d^{0}4s^{0}\; No unpaired electron
Mn2+–  3d54s0  \mathrm{Mn}^{2+} \text{--}\; 3d^{5}4s^{0}\; 5 unpaired electrons
Fe3+–  3d54s0  \mathrm{Fe}^{3+} \text{--} \; 3d^{5}4s^{0} \; 5 unpaired electrons
Co2+–  3d74s0  \mathrm{Co}^{2+} \text{--}\; 3d^{7}4s^{0}\; 3 unpaired electrons
Out of these only Cu+\mathrm{Cu}^{+}and Sc3+\mathrm{Sc}^{3+} are colourless. All other ions are coloureddue to presence of unpaired electrons.
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