Nitride Ion is a type of compound wherein the charge of Nitrogen is -3. This is considered to be a very basic type of compound. This usually undergoes protonation almost immediately which explains why this is not commonly encountered by those who normally work with different types of compounds.
Its official formula is N3. For those who would like to know more about the Nitride Ion, it should be remembered that this has 7 protons, 8 neutrons, and 10 electrons. This is just one of the many compounds that you can study when you take up chemistry.