oxidation numbers

[Alison Trinh 1E]

How do you find the oxidation numbers of elements to balance redox reactions?

[Katie Kyan 2K]

You have to check the overall charge of the compound in order to find the oxidation number of the elements. For example for MnO4-, we know that the charge of oxygen is 2- so with four oxygens this makes up a charge of 8-. The overall charge of the compound is 1- so that means the charge of Mn must be 7+.

[kennedyp]

I found a really good video explaining how to find them if you have the time to watch before Final real quick! I post the link below. Good luck! https://www.youtube.com/watch?v=-a2ckxhfDjQ

[Hui Qiao Wu 1I]

There are some basic ones that you'll just have to remember:
hydrogen is +1 when bound to nonmetal but is -1 when bound to a metal
oxygen in the form of O^2 is -1; all other forms are -2

[Aiden Metzner 2C]

Count the oxygens and hydrogens in the molecule. The oxygens are -2 and the hydrogens are +1, the other element in the molecule will add to these elements to get the molecule to whatever charge it is.