Number of electrons

[Brandon Mo 4K]

How do we determine the number of electrons in the oxidation and reduction half-reactions?

[Kevin ODonnell 2B]

In half reactions we just find the sum of the two halves (the reduction half-reaction + the oxidation half-reaction). First make sure all of the equations are balanced. Make sure in molecule compounds as well that you are taking note of the sign. For example, let's pretend that FeO₂^-2 is a thing. We know O has a charge of -2 and -2 * 2 atoms = -4 charge, so we can deduce Fe has a initial charge of +2, and if it is oxidized we will see that it has a +3 charge on the product side.
As far as half reactions go I will attach an easy example:

[Bruce Chen 2H]

We want to balance the number of electrons on both sides. In order to do this, we must add electrons in the half reactions. They should cancel out when added.

[204929947]

In adittion, how would you find out the oxidation number of an element??

[Celine Cheng 1H]

For the oxidation numbers question, you generally want to look at the charge of the element/compound. The sum of the oxidation numbers of the elements in a compound should equate to the compound's overall charge. There are some specific rules for finding oxidation numbers of certain elements, which you can find here: https://www.khanacademy.org/science/che ... ion-number

[Jocelyne Milke 1G]

you can find the oxidation numbers using the periodic table