Why and how does nitrogen have oxidation states from -3 to +5?
Ulex writes You must remember that oxidation number is only a book-keeping exercise – keeping track of the electrons used in bonding. The outcome is not necessarily related to numbers of bonds formed. You are probably concerned because you know that the nitrogen atom cannot use all of its five outer electrons for single covalent bond formation. This is because, at the second quantum level, there are no d orbitals to put the extra electrons in. This is true but, because the nitrogen atom can use its lone pair to form a dative bond, the outcome often looks as though nitrogen is doing more than its should be able to. In NH4Cl, to take an obvious case, the nitrogen atom appears to be forming 5 bonds, and it is in fact doing so (3 ordinary covalent, 1 dative and 1 ionic), but its oxidation number is still only +3. In nitric acid, HNO3, and in the nitrate ion NO3-, the nitrogen atom does have an oxidation number of +5 but it does not form 5 covalent bonds. It does form 1 double bond to oxyge
