Question

Which of the following compounds is/are coloured?

• A. $C{u}_{2}C{l}_2$
  
• B. $TiC{l}_4$
  
• C. $Ce(S{O}_4{)}_2$
  
• D. $KMn{O}_4$
  

Answer 1

Answer: (C), (D)

$KMn{O}_4$


Generally transition elements and their salts are coloured due to the presence of unpaired electrons in metal ions.

($KMn{O}_4$) is colored because it absorbs light in the visible range of the electromagnetic spectrum. The permanganate ion is the source of the color, as a ligand-to-metal charge transfer takes place between the oxygen's p-orbitals and the empty d-orbitals on the metal.

Electronic configuration of
$Ce=\left[Xe\right]4f^{1}5d^{1}6s^2$
$C{e}^{+2}=\left[Xe\right]4f^{1}5d^1$
Since it has unpaired electrons , $Ce\left(S{O}_4\right)$ exhibits yellow colour.