Nomenclature of inorganic compounds

As depicted in books, $\ce{NO3-}$ and $\ce{NO2-}$ are called as nitrate and nitrite respectively. Where (-ate) suffix is used for higher oxidation state and (-ite) suffix is used for lower oxidation state (just like:- sulfate and sulfite). 


Now since Nitrogen is 2nd period element, hence it can't expand it's octet (no vacant d-orbital). So I didn't get how (-ite or -ate) suffix can be used if nitrogen shows only 1 stable oxidation state i.e; (+3). Can anyone suggest?




Nitrogen can have a variety of [oxidation states](http://chemwiki.ucdavis.edu/Organic_Chemistry/Amines/Properties_of_Amines/Oxidation_States_of_Nitrogen) ranging from -3 to +5. For example:



> 
> -3
> 
> 
> 


The nitrogen atom in ammonia $\ce{NH3}$ has an oxidation state of -3 (each hydrogen is +1).



> 
> -2 
> 
> 
> 


The nitrogen atoms in hydrazine $\ce{N2H4}$ has an oxidation state of -2.



> 
> 0
> 
> 
> 


The oxidation state of the nitrogen atoms in $\ce{N2}$ is 0.



> 
> Nitrate and nitrite
> 
> 
> 


The nitrogen atom in the nitrate ion $\ce{NO3-}$ has an oxidation state of +5. Each oxygen atom has an oxidation state of -2, and the overall charge on the ion is -1. 


The nitrogen atom in nitrite ion $\ce{NO2-}$ has an oxidation state of +3.


Nitrogen can have such a range of oxidation states because of its electron configuration, which is $\ce{[He]}2s^2 2p^3$ (5 valence electrons). Nitrogen can "gain" up to three electrons or "lose" up to five electrons.


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