Chemistry - Coordination Chemistry Question with Solution | TestHub
When an electron from a lower energy d orbital is excited to a higher energy d orbital, the energy of excitation corresponds to the frequency of light absorbed. This frequency generally lies in the visible region.
The color observed corresponds to the complementary color of the light absorbed.
Consider an aqueous solution of the complex of a 3d-series metal ion: ²⁻, ²⁺, and ²⁺ are have different colour ; one of them is red other are yellow and blue.
Select which complex ion is blue & yellow respectively :
Options:
Answer:
Solution:
The color of complex ions depends on the ligand field splitting energy. Strong field ligands (like NH₃) cause larger splitting, absorbing higher energy light, while weak field ligands (like Cl⁻) cause smaller splitting, absorbing lower energy light.
For Ni²⁺ complexes:
is yellow (absorbs blue/violet light).
is blue (absorbs orange/red light).
Thus, option A is correct.
Concepts: Ligand field theory, d-d transitions, spectrochemical series.