The maximum oxidation state shown by Nitrogen is
-3
+3
+4
+5
The highest possible oxidation state for the non metals is equal to the total number of electrons present in the valence shell of the atom. As N has 5 electrons in its valence shell so its maximum oxidation state is +5.
It shows its +5 oxidation state in compounds like and
.
Therefore, option (4) is correct.