Question

Which of the following compound is expected to be coloured?

• A. $A{g}_{2}S{O}_4$
• B. $Cu{F}_2$
• C. $Mg{F}_2$
• D. CuCl

Answer 1

Answer: (B)

$Cu{F}_2$

$A{g}_{2}S{O}_4$ contain $A{g}^{+}$ ion having outer electronic configuration of $4d^{10}$ with 0 unpaired electrons and is colourless.
$Cu{F}_2$ contains $C{u}^{2+}$ ion having outer electronic configuration of $3d^9$ with 1 unpaired electron and is coloured.

$Mg{F}_2$ contains $M{g}^{2+}$ with 0 unpaired electrons having outer electronic configuration of $3s^2$ and is colourless.
$CuCl$ contains $C{u}^{+}$ ion having outer electronic configuration of $3d^{10}$ with 0 unpaired electrons and is colourless.

Hence, option $B$ is correct.