Question

I having the worst time trying to understand how to assign oxidation numbers to things, and then determine how the oxidation numbers change. I would like to understand how to assign oxidation numbers to elements or molecules. Is there a way to do this in a simple way, or is it always so complicated?

Answer 1

Some key points when assigning oxidation numbers:

1. Use a periodic table, most of the elements only have one or two oxidation numbers, so just look for them up in the periodic table.

2. You can also use an "inverse" of the criss cross method. Once given a formula, you can use criss cross method to assign oxidation numbers. For example, assign the oxidation numbers of Al₂O₃:

The oxidation number of O is -2 and the oxidation number of Al is +3.

3. Another tip you can use is to check if the net charge of the given compound is 0, or in case it is an ion, check if the given charge is actually fulfilled.

Those are the main tips I use to assign oxidation numbers.