Oxidation state

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104922499 1F
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Joined: Fri Sep 29, 2017 7:04 am

Oxidation state

Postby 104922499 1F » Tue Feb 20, 2018 1:52 pm

what is an easy way to figure out the oxidation states?

Angela 1K
Posts: 80
Joined: Fri Sep 29, 2017 7:05 am

Re: Oxidation state

Postby Angela 1K » Tue Feb 20, 2018 2:21 pm

There are a couple standard rules that will help determine the oxidation states of certain atoms in molecules.

Hydrogen always has a +1 oxidation state.
Oxygen almost always has a -2 oxidation state (unless its with H2O2).

Let's find out the oxidation state of oxygen in H2O2 as an example.
We know that hydrogen has a +1 oxidation state, and the overall charge on the molecule is 0. If we were to assign "x" to the oxidation state of oxygen, we would get +1(2) because we have 2 hydrogen atoms and 2x because we have 2 oxygen atoms.
+1(2) + 2x = 0
When we solve it out, we get that x = -1, and so the oxidation state of oxygen in this molecule is -1.

Here's another example:
MnO4-
We can assume that the oxidation number of oxygen is -2. The overall charge of the molecule is -1. Thus, the math we have to solve for is x + 4(-2) = -1.
When solving for x, we get x = +7, and so the oxidation state of manganese in this example is +7.

Hope this helps!

Anne 2L
Posts: 35
Joined: Fri Sep 29, 2017 7:05 am

Re: Oxidation state

Postby Anne 2L » Tue Feb 20, 2018 2:38 pm

Assuming your asking about assigning oxidation numbers, there are a few rules to follow.

1) atoms in their natural state are assigned 0 (e.g., Al, H2)
2) monatomic ions are assigned their charge (e.g., Na+ = +1)
3) neutral compounds are assigned 0 (e.g., CO2)
4) polyatomic ions are assigned their overall charge (e.g., NH4+ = +1)
5) Group 1 atoms in a compound are assigned +1 (e.g., Li = +1)
6) Group 2 atoms in a compound are assigned +2 (e.g., Mg = +2)
7) oxygens in a compound are usually assigned -2 (e.g., H2O)
8) oxygens in any peroxide are assigned -1 (e.g., H2O2)
9) oxygens paired to fluorine are assigned +2 (e.g., OF2)
10) hydrogens in a compound are usually assigned +1 (e.g., H2O)
11) hydrogens in binary metal hydride are assigned -1 (e.g., LiH)
12) fluorines are always assigned -1
13) chlorine, bromine, and iodine are assigned -1 unless paired with fluorine or oxygen

I think that's all of them. A lot of the rules are usually grouped together. I was just trying to be as clear as possible.

104922499 1F
Posts: 53
Joined: Fri Sep 29, 2017 7:04 am

Re: Oxidation state

Postby 104922499 1F » Tue Feb 20, 2018 6:10 pm

why is O3's oxidation state 0?

soniatripathy
Posts: 50
Joined: Thu Jul 13, 2017 3:00 am

Re: Oxidation state

Postby soniatripathy » Wed Mar 14, 2018 3:51 pm

I found that this video is pretty comprehensive (and shorter than the other response) and gives you the most used rules of assigning oxidation numbers: https://www.youtube.com/watch?v=-a2ckxhfDjQ&t=61s
Hopefully this helps!

Rachel Wang
Posts: 49
Joined: Fri Sep 29, 2017 7:04 am

Re: Oxidation state

Postby Rachel Wang » Fri Mar 16, 2018 5:27 pm

104922499 1F wrote:why is O3's oxidation state 0?


It's a triatomic gas with the same element -> no oxidation state

704887365
Posts: 49
Joined: Sat Jul 22, 2017 3:00 am

Re: Oxidation state

Postby 704887365 » Fri Mar 16, 2018 7:45 pm


Seth_Evasco1L
Posts: 54
Joined: Thu Jul 27, 2017 3:00 am

Re: Oxidation state

Postby Seth_Evasco1L » Fri Mar 16, 2018 8:27 pm

What would the oxidation state of I3- be?


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