Examples

In this post, we will determine the oxidation numbers in the sulfate ion – SO42-.

To determine the oxidation number of an atom(s) in a molecule or an ion, start with the known oxidation numbers and the rules summarized below:

 

 

Keep in mind that the summary is zero for neutral molecules and is equal to the charge for ions.

For SO42-, the element with a standard oxidation state is oxygen which is -2, and we need to determine the oxidation state of the sulfur. 

Rule 8 – The oxidation of oxygen is -2:

Assign x for the oxidation state of S and set up an equation:

x + 4(-2) = -2, X = +6

 

Further Reading

 

More examples of the oxidation state in this multiple-choice quiz:

Free

Oxidation State and Redox Reactions Quiz

Free

Reactions in Aqueous Solutions Quiz

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