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# Oxidation number confusion of nitrogen. watch

1. in HNO3, why does nitrogen have the oxidation state of +5 and not +3?

Why does this occur and how do you know when it is in a +3 or +5 state?

+rep too

Thanks
2. The rules you need to know are oxygen nearly always has an oxidation state of -2 (if not a peroxide or superoxide). Hydrogen nearly always has an oxidation state of +1 (if not a hydride). In order to have an overall oxidation state of 0 (which all neutral molecules have) the nitrogen must be +5.
3. (Original post by Kyri)
The rules you need to know are oxygen nearly always has an oxidation state of -2 (if not a peroxide or superoxide).
Or if O is bonded with F, in which case it can have an oxidation number of +1 or +2. So all in all: O normally has -2, but this takes priority behind F having -1, H having +1 and the Group 1 metals having +1, so that in cases where you have only O and one of these 3 (F, H or a Group 1 metal) O can have a -1(peroxide) or -1/2 (superoxide) oxidation number.
Or if O is bonded with F, in which case it can have an oxidation number of +1 or +2. So all in all: O normally has -2, but this takes priority behind F having -1, H having +1 and the Group 1 metals having +1, so that in cases where you have only O and one of these 3 (F, H or a Group 1 metal) O can have a -1(peroxide) or -1/2 (superoxide) oxidation number.
hi, so because in HNO3, the addition of oxygen is -6 (-2*3). but because hydrogen is always (or most times) +1, it goes down to -5, right?, therefore N would have to be +5 to get to 0, right.

Note, is the oxidation state of oxygen in in HNO3 -6, or is it -2 (-6/3)?
5. (Original post by Kyri)
The rules you need to know are oxygen nearly always has an oxidation state of -2 (if not a peroxide or superoxide). Hydrogen nearly always has an oxidation state of +1 (if not a hydride). In order to have an overall oxidation state of 0 (which all neutral molecules have) the nitrogen must be +5.
What do you mean by not a hydride?
6. (Original post by Hi, How are you ?)
hi, so because in HNO3, the addition of oxygen is -6 (-2*3). but because hydrogen is always (or most times) +1, it goes down to -5, right?, therefore N would have to be +5 to get to 0, right.

Note, is the oxidation state of oxygen in in HNO3 -6, or is it -2 (-6/3)?
You don't take the sum of the atoms, you take the average. Oxygen is -2, as usual...
7. (Original post by Hi, How are you ?)
in HNO3, why does nitrogen have the oxidation state of +5 and not +3?

Why does this occur and how do you know when it is in a +3 or +5 state?

+rep too

Thanks
In HNO3 the oxygen has a state of -2. There are 3 oxygens so you multiply the state by the three so oxygen is -6. The hydrogen has a +1 charge. When adding both states together you get -5. The overall charge on the molecule is 0 so you then know that the nitrogen is +5. Hope this makes sense!
8. (Original post by Hi, How are you ?)
What do you mean by not a hydride?
You can get compounds where the H is bonded directly to an alkali metal like NaH (sodium hydride) where the oxidation state of H is -1. I don't know if you'd encounter them in your course but I mentioned it as I predicted someone would come along and tell me that H isn't always +1.
9. (Original post by Hi, How are you ?)
hi, so because in HNO3, the addition of oxygen is -6 (-2*3). but because hydrogen is always (or most times) +1, it goes down to -5, right?, therefore N would have to be +5 to get to 0, right.

Note, is the oxidation state of oxygen in in HNO3 -6, or is it -2 (-6/3)?
The oxidation number of an element in the compound is the average. So it's -2. That's what we meant when we said O usually has an oxidation number of -2: it doesn't matter how many there are, it'll always (usually) come out the same.

As for thinking, yes, it's spot on. Short of calculating it properly, that's the same way I tend to think about it. e.g. Here's a tough example:

[CuYAs3O6]2- - given that Cu has an oxidation number of +2 and Y has +4, what is the As oxidation number?

Spoiler:
Show
You should get +(4/3). It's the average, remember.

BTW, don't ask me anything about that ion's properties, I completely made it up just for this example!
10. (Original post by Hi, How are you ?)
in HNO3, why does nitrogen have the oxidation state of +5 and not +3?

Why does this occur and how do you know when it is in a +3 or +5 state?

+rep too

Thanks
use algebra to find oxidation numbers

H always has an ox number of +1 and O nearly always has one of -2

Let N = x

There Easy as that. Just gotta remember that Oxygen always has an Oxidation number of -2 (except in a few cases) and Hydrogen +1 and Group 1 metals +1 and group 2 metals +2!
11. the rifles of the iraaaaa

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