Question

Generally metal iron and their salts are coloured due to presence of unpaired electrons in metal ions. Which of the following compounds are coloured?

• A. $Ce(S{O}_4{)}_2$
• B. $TiC{l}_4$
• C. $C{u}_{2}C{l}_2$
• D. None of these

Answer 1

The correct option is A $Ce(S{O}_4{)}_2$

${Ce\left({SO}_4\right)}_2$ is coloured. If it has unpaired electrons

${Ce}^{4+}$ is central metal atom

$\downarrow$

${Ce}^{4+}(Z=58)\to \left[Ar\right]{3d}^{10}{4P}^6{5S}^2{4d}^{10}{5P}^6{6S}^2{4f}^2$

$\left[Ar\right]{3d}^{10}{4P}^6{5S}^2{4d}^{10}{5P}^4{6S}^0{4f}^2$

unpaired electrons $=n=4$

$\to$ Coloured due to presence of unpaired $e^{-}s$.