Number of electrons

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Brandon Mo 4K
Posts: 70
Joined: Fri Sep 28, 2018 12:15 am

Number of electrons

Postby Brandon Mo 4K » Fri Feb 22, 2019 1:16 am

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

Kevin ODonnell 2B
Posts: 62
Joined: Fri Sep 28, 2018 12:24 am

Re: Number of electrons

Postby Kevin ODonnell 2B » Fri Feb 22, 2019 4:26 am

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:
Screen Shot 2019-02-22 at 4.26.14 AM.png

Bruce Chen 2H
Posts: 60
Joined: Fri Sep 28, 2018 12:26 am

Re: Number of electrons

Postby Bruce Chen 2H » Fri Feb 22, 2019 2:31 pm

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.

Posts: 76
Joined: Fri Apr 06, 2018 11:03 am

Re: Number of electrons

Postby 204929947 » Fri Feb 22, 2019 3:34 pm

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

Celine Cheng 1H
Posts: 33
Joined: Fri Sep 28, 2018 12:21 am
Been upvoted: 1 time

Re: Number of electrons

Postby Celine Cheng 1H » Fri Feb 22, 2019 3:57 pm

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: ... ion-number

Jocelyne Milke 1G
Posts: 73
Joined: Fri Sep 28, 2018 12:25 am

Re: Number of electrons

Postby Jocelyne Milke 1G » Fri Feb 22, 2019 5:14 pm

you can find the oxidation numbers using the periodic table

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