A model for the aeronomy of odd nitrogen in the thermosphere is constructed that satisfactorily describes published measurements of odd nitrogen species. On the basis of theoretical considerations of the molecular processes associated with N2 ++O→NO++N and N2 dissociation by electron impact and EUV radiation between 800 and 1000 ¿, we argue that essentially every reaction of N2 ++O leads to the formation of N(2D) and that the latter processes proceed through the same intermediate states which predissociate to form one N(2D) and one N(4S) atom. The model predicts NO Δ (O,O) band emission, in good agreement with the measurements by Feldman and Takacs (1974).