Spectroscopic diagnostics for the N III ion have been studied using an atomic model comprising of the first eleven energy levels. We have taken account of the various populating and depopulating mechanisms to solve the detailed balance equations to determine the level populations as a function of electron density and temperature. We then studied the line emissivity ratios as tools for density and temperature diagnostics. Density-sensitive and temperature-sensitive line emissivity ratios have been presented and their diagnostic applications to the solar atmosphere have been discussed with the help of available observations.