Question

The colour of $K_{2}C{r}_2{O}_7$ 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

$K_{2}C{r}_2{O}_7$, 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 (LMCT) occurs.

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