Question

the ion which is coloured not due to d-d transition ,is ​

Answer 1

For example, the orange colour of TiBr4, yellow colour of CrO42– , orange colour of Cr2O2–7, intense red colour of [Fe(SCN)4] and deep purple of MnO4 are not due to d—d transitions. In the case of MnO4 ion, the color is due to charge transfer and not due to d-d transitions.

Answer 2

Ions that have unpaired electrons in their d-orbitals are coloured due to d-d transitions.

• Ions with unpaired electrons can absorb certain wavelngths of light and get excited , when the excited ions come back to normal state they emit light of certain wavelengths.
• These light emmited is what we identify as the colour of the ion.
• An example of an ion showcasing colour due to d-d transition is [NiCl4](2-).