Question

Co -ordination compound exhibits color. This can be attributed with:

Answer 1

Coordination compounds are those compounds which make the complex ion structure in which all the ligands are attached to the central metal atom through the coordinate bond. The central metal is generally the $d -$ block element which have unpaired electrons present in the $d -$ subshell. The exhibition of colour can be explained on the basis of these electrons.

Complete answer:
The coordination compounds generally do exhibit colour when there is excitation of electrons. Also the colour exhibited by these compounds is attributed to the crystal field theory which corresponds to the $d - d$ transition of the elements. The interaction between the central metal atom and the ligand is explained by the crystal field theory. The metal and ligand are bonded ionic according to this theory. When the transition metals are not bonded to any ligand then the $d -$ orbitals are degenerate which means they give the same energy. But when a ligand is bonded with the central metal atom and due to the different symmetries of $d -$ orbitals and the inductive effect produced by ligands on the electrons of the orbitals the $d -$ orbitals get split and become non-degenerate. Now when the $d - d$ transition of electrons takes place then they show colour. Whenever there is a transition of electrons the complex will show the colour.

Note:
Ligands are the molecules which are attached to the central metal atom through coordinate bonds. Coordination compounds also exhibit colour in their aqueous solution. The crystal field splitting is responsible for the cause of colour exhibition of these complexes. There will be transition whenever a strong ligand approaches the central metal atom and thus it has great inductive effect.