Oxidation Numbers

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Jessica Esparza 2H
Posts: 130
Joined: Wed Sep 18, 2019 12:15 am

Oxidation Numbers

Postby Jessica Esparza 2H » Fri Feb 21, 2020 3:50 pm

Does anyone have any tips for finding oxidation numbers?

Cooper Baddley 1F
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Joined: Wed Sep 18, 2019 12:19 am

Re: Oxidation Numbers

Postby Cooper Baddley 1F » Fri Feb 21, 2020 4:00 pm

Break the molecule into each of its elements. Then use a periodic table to find the normal charge of each element. Then combine those to find the oxidation number.

Daniel Toscano 1L
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Joined: Tue Nov 13, 2018 12:18 am

Re: Oxidation Numbers

Postby Daniel Toscano 1L » Fri Feb 21, 2020 4:11 pm


Verity Lai 2K
Posts: 100
Joined: Sat Aug 24, 2019 12:18 am

Re: Oxidation Numbers

Postby Verity Lai 2K » Sat Feb 22, 2020 11:05 am

The oxidation number is the charge of the element which you can find from patterns on the periodic table. For example, group 1 has an oxidation number/charge of +1.

Angela Patel 2J
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Joined: Sat Aug 24, 2019 12:17 am

Re: Oxidation Numbers

Postby Angela Patel 2J » Sat Feb 22, 2020 11:15 am

We know common oxidation numbers. For example oxygen always has an oxidation number of 2-. Hydrogen is typically +1. All group 1 metal cations have a charge of +1, etc. You can use these known oxidation numbers to find the oxidation numbers of other elements in compounds with these.

Dina Marchenko 2J
Posts: 54
Joined: Thu Jul 25, 2019 12:16 am

Re: Oxidation Numbers

Postby Dina Marchenko 2J » Sat Feb 22, 2020 9:54 pm

You're best off memorizing the main rules (ex: O2 is always -2 for this class, group 1 are +1, etc.)

When looking at a compound, first look at the elements that have oxidation number rules and figure out what the oxidation number of a single atom would be. Then multiply that by any subscript or stoichiometric coefficients to get the overall charge of that subunit (if it's cl2, within a compound then the overall charge would be -2 not -1). Once you know this, you can find the oxidation number of the other element(s) of the compound (usually this will be the transition metal). Find a number that combines with the charge you just found to equal the overall charge of the compound (neutral or -1 or +1 or whatever it is). For main group elements (not d block metals) the oxidation number will often coincide with the group number.

Just taking it one step at a time and being precise.

Charlene Datu 2E
Posts: 62
Joined: Wed Sep 11, 2019 12:16 am

Re: Oxidation Numbers

Postby Charlene Datu 2E » Sun Feb 23, 2020 12:18 am

I would also break down the molecule, like someone said previously. By using the periodic table, you can determine the formal charges for the well-known elements. However, for the other elements that you don't know as well, you can find it based off of the other elements in the molecule. The overall charge of the molecule should equal the sum of the charges of all of the elements.

Manav Govil 1B
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Joined: Sat Sep 07, 2019 12:19 am

Re: Oxidation Numbers

Postby Manav Govil 1B » Sun Feb 23, 2020 12:20 pm

The oxidation numbers for metals in their natural states are their charges, I believe.

Radha Patel 4I
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Joined: Tue Feb 12, 2019 12:15 am

Re: Oxidation Numbers

Postby Radha Patel 4I » Sun Feb 23, 2020 12:29 pm

I like to set it up as if it were an algebraic expression. For example, if we want to find the oxidation number of S in SO4^2-we can set it up algebraically. We know that the overall molecule has to equal -2 and that oxygen has an oxidation number of -2. There are 4 oxygens so we multiply 4 by -2 to get the oxidation number of oxygen. Since S is unknown, we can find it through this equation with S as a variable: S+ 4(-2)=-2 . If we solve for S , we get S=6+ , so 6+ is the oxidation number of S.

Connor Chappell 2B
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Joined: Wed Feb 20, 2019 12:16 am

Re: Oxidation Numbers

Postby Connor Chappell 2B » Sun Feb 23, 2020 12:32 pm

Many of the compounds that we deal with in redox reactions contain oxygen, hydrogen, and/or a transition metal, as well as common group 1 elements. Memorizing that Oxygen is 2- and the group 1 elements are +1 can help you identify the oxidation states of the other elements in the compound.


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