Question

The colour of $K_{2}C{r}_2{O}_7\text{and}F{e}^{2+}$ ions are respectively due to :

• A. d-d transition and charge transfer spectra
• B. charge transfer spectra and d-d transition
• C. crystal defects and charge transfer spectra
• D. charge transfer spectra and crystal defects

Answer 1

The correct option is B charge transfer spectra and d-d transition

charge transfer spectra and d-d transition $K_{2}C{r}_2{O}_7$ shows colour due to a charge transfer because the oxidation state of $Cr$ is $+6$ , so there are no d- electrons which can be excited. Therefore, the colour is due to charge transfer. Here, ligand to metal charge transfer $\left(LMCT\right)$ occurs.

$F{e}^{+2}$ has 6d-electrons, so the colour is due to d - d transitions.