Question

Why is the highest oxidation state observed for${\mathbf{CrCl}}_{\mathbf{4}}$ only the+4 oxidation state, in contrast to the+6 state observed in ?

Short answer

F^-has a higher charge density due to a smaller size ofF^- and are stable with +6 oxidation state, and it is stabilized by high charge density.

Chloride is a weak field ligand , and there is inter ligand repulsion. Hence it does not go for +6 oxidation state.

Step-by-step solution

Oxidation state

The oxidation state is denoted using numbers that are positive, negative or zero.The oxidation state is found after the element name and is indicated by a Roman numeral in inorganic nomenclature.

Different oxidation states observed for CrCl4 and  CrF6

F^- has a higher charge density due to a smaller size of and are stable with +6 oxidation state, and it is stabilized by high charge density. Thus, the compound${\text{CrF}}_{\text{6}}$ is possible. On the other hand, chloride is a weak field ligand, and there is inter ligand repulsion. Hence it does not go for +6 oxidation state. So the compound${\text{CrCl}}_{\text{4}}$ is more stable with an oxidation state of +4.