Question

Which one of the following ions will give a coloured solution?

• A. $Cu^{+}$
• B. $Fe^{2 +}$
• C. $Zn^{2 +}$
• D. $Ag^{+}$

Answer 1

Answer: (B)

Since $Fe^{2 +}$ has unpaired electrons so, d-d transitions would take place and hence, its solution would be coloured.
$Cu^{+} \rightarrow 3d^{10}$
$Fe^{2 +} \rightarrow 3d^{6}$
$Zn^{2 +} \rightarrow 3d^{10}$
$Ag^{+} \rightarrow 4d^{10}$