Charge on ligands? [ENDORSED]

[Rebecca Chu 1C]

How do you find the charge on ligands and the oxidation # if you're only given the overall charge of the molecule. I thought you needed to know both the overall charge and charge on all ligands to find the oxidation #.

[hannahtweedy]

Don't you find the oxidation of the metal then match it equally and with an opposite charge for the ligand?

[Joanna Pham - 2D]

It would help to know the charges on the ligands. There's a chart on page 742 that gives you all the common ligands and their charges. Once you know the overall charge on the ligand, to find the oxidation number of the transition metal, then you would need to see what number added to the ligand charge would give the same number as the overall charge on the molecule. So like oxidation # + ligand charge = overall charge on coordination compund.

For instance, say you have something like [Cr(en)]^3+. en stands for ethylenediamine, and it has a neutral charge (which is given in the chart on page 742). Since the overall charge on the coordination compound is +3 and the ligand charge is 0, then the oxidation number for Cr would be +3