[Rutherford]

How to solve the attached problem?

I know that the cyanide group will cause the biggest splitting 26,600, but what about the rest? Why has CrF₆^2- a bigger splitting than Cr(H2O)₆³⁺? I know that they have different oxidation states of Cr, but how does it cause the difference?

[kriggy]

The oxidation number of metal atom is also involved in splitting of D orbitals. So if we say that Δof M²⁺ is 1 then Δ for M³⁺ is about 1,6 and for M⁴⁺ its 1,9.
Im not sure why is that I cant find it in any of my notes, so if anyone knows plz share

[Rutherford]

Difference in ligand nature vs. the difference in oxidation number. Which one will prevail, I don't think is easy to tell.

[kriggy]

They both are involved  so if you have [M(CN)₆]^2- and [M(CN)₆]^3- and M is the same metal then [M(CN)₆]^2- will have greter value of Δ. Or at least according to my book

[Rutherford]

Okay. Now, I could just use some explanation why is it so.

[kriggy]

Ok found it:
By increasing the oxidation number of cental atom (and its positive charge) you also increase the atraction between nucleus and electrons in ligands which then increase the repulsion between the electrons in ligands and electrons in central atom and then the Δ.

[Rutherford]

Good. Thank you.