Oxidation number

[Tianna Nguyen 1I]

How do we find the oxidation number of the metal ion? Do we use the formal charge equation?

[205686400]

Hi! Not exactly. The formal charge formula should only be used when looking for the formal charge of each individual molecule/atom which is not to be confused with the oxidation state. The oxidation state depends on the oxidation state of every molecule within your complex. For example, if your complex is [TiF(NH3)5]+ you'd first label your Ti as the metal, the F and NH3 as your ligand molecule, and the + at the end as your overall oxidation state. Now we look at oxidation state of the ligand molecules and we know that NH3 has a oxidation state of 0 and that Fluorine has a oxidation state of -1. From here its basic math as you want to use the metal charge to counter the negative fluorine and have an overall oxidation state of +1. Since 2-1=1 we have determined that 2 or (II) is the oxidation state of the metal.

[Jacqueline Musico 3A]

Ligands are always either neutral or negatively charged. As a result, the metal cation will always have a positive oxidation number. To find it, go through the ligands and determine if they are neutral or negatively charged. Then, look at the anions outside the coordination sphere and determine their oxidation states. Remember that group 17 is (-1) ,and oxygen is almost always (-2). The oxidation number of the cation will be the absolute value of the total negative oxidation state from the ligands/anions so that the total charge on the coordination compound is 0.

[Ananya Sridharan]

You can find the oxidation number of a metal ion by using the known oxidation numbers/charges of the rest of the molecules in the equation. All the oxidation numbers in a molecule must add up to equal the overall charge. And we know certain compounds are neutral and some have a charge. Using these charges, we can determine an unknown metal ion oxidation number.

[Kayla Ziebell 1H]

How I go about finding the oxidation number of a metal ion is by first finding the formal charges of all the ligands in the compound both inside and outside the bracket. If the compound has a neutral charge, then the metal ion takes on the formal charge with an opposite sign as the total in order to make the entire compound neutral. If it has a -2 charge, the metal ion would have a +2 charge.
If the ligands take on a -4 charge and the entire compound has a formal charge of -2, then metal ion would have a +2 charge.