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 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.
