Here's the question you clicked on:
DLS
What on earth is the oxidation number of N in N2H4?
Each bond with H gives 2 electrons to the N |dw:1359301726739:dw|
|dw:1359301793906:dw| The N's are equal so 1 electron to each
Now each N has 7 electrons, can you figure out the oxidation number?
It has extra electrons, so it's negative, so yes, -2 :)
answer=+2 thats what confuses me
OK i was a bit confused, here this explanation is better : http://answers.yahoo.com/question/index?qid=20071023171027AA07wRO
i didnt get t hat explanation,sry
Aere you sure it's +2? I'm pretty sure it's -2...
Well the way the guy on Yahoo Answers is solving it is like this: The overall state of the Hydrogens is -4, since each hydrogen gives -1 when bonded to a non-metal. The overall state of the entire molecule is 0 (no charge). So the overall state of the N's must balance out with the overall state of the H's to give 0. So the overall state of the N's must be +4, since -4+4 = 0. Since there are 2 N's, each N is +2
When you have to determine the oxidation numbers in a molecule, imagine dividing it into ions. The electrons always go to the element with the higher electronegativity. In this case H has electronegativity 2.1 and N was 3.0 so N gets all the electrons. As a result H has an oxidation number +1 (with no electrons left) and N has -2 (with 7 electrons). It seems the answer is mistaken in the book. Btw the guy on Yahoo was switched it around. H was +1 when bonded to a non-metal and -1 when bonded to metal.
http://www.chacha.com/question/what-is-the-oxidation-state-of-nitrogen-in-n2h4
@DLS: About your link: either that's the same Yahoo guy answering or somebody has copied his answer. The wording is pretty much the same. I could link you to a German site where the oxidation number of N is -2 (scroll down to Hydrazin, there's a picture): http://www.guidobauersachs.de/oxi/oxi.htm. They don't explain the determination of the oxidation number there so the language shouldn't be a problem. I'm not trying to convince you with internet links though. They can always be wrong. What matters in this case is the electronegativity principle.
It can be a matter of definition, but that should not be. In your compound, oxidation number of N is -2, as far as France is concerned.