Question

Which of the compound is both paramagnetic and coloured ?

• A. $Cu{F}_2$
• B. $K_3\left[Cu\right(CN{)}_4]$
• C. $K_2\left[TiC{l}_6\right]$
• D. $K_{2}Cr{O}_4$

Answer 1

The correct option is A $Cu{F}_2$

$Cu{F}_2(d^9,C{u}^{2+})$ is both coloured and paramagnetic due to the presence of unpaired electron.
However, the following two compounds are colourless due to the absence of unpaired electrons.
$K_3\left[Cu\right(CN{)}_4]$ is colourless $(C{u}^{+},d^{10})$ and diamagnetic
$K_2\left[TiC{l}_6\right]$ is colourless $(T{i}^{+4},d^0,)$ and diamgnetic.
However, the compound $K_{2}Cr{O}_4$ is yellow although it has no unpaired electron and therefore, is diamagnetic. It is coloured due to the charge transfer $(C{r}^{+6},d^0)$.

Hence, option A is correct.