Assigning Oxidation Numbers

[Olivia D 3B]

Does anyone have a good conceptual explanation or a general summary of the rules needed to correctly assign oxidation numbers to the different elements within a compound?

[Jenny Han 3F]

There are a lot of rules, but some general ones include that cations are written before anions, like in NaCl. For compounds, the oxidation number tends to follow the tendency for a charge (gaining or losing electrons) from the periodic table. For example, Group IA elements tend to have a +1 oxidation number. Single atoms or ions tend to have the oxidation number of their charges (if none, then 0). Normally, oxygen and hydrogen have oxidation numbers of -2 and +1 respectively (there are exceptions!). The sum of oxidation numbers of the atoms in a compound that is overall neutral is 0, while for a polyatomic ion it adds up to its charge.

[Katelyn Alvarado 3K]

Some other rules that haven't been mentioned already are that O has an oxidation # of -1 when it is a peroxide. Other than that, it's -2. Hydrogen has an oxidation # of +1 when bound to nonmetals and -1 when bonded to metals. Flourine is always -1. Halogens have variable oxidation states when bound to oxygen but other than that they are -1.