Silver nitrate is a chemical compound with the formula AgNO3. It is composed of the silver cation (Ag+) and the nitrate anion (NO3-). Silver cations are very sensitive to light and were commonly used in the photography process in the days of photosensitive films (in other words, before digital photography). Silver nitrate, however, is not quite as sensitive to light as other silver salts.
Silver nitrate is a pretty stable chemical compound. When exposed to atmospheric oxygen (O2), it really does nothing. I suppose that if you heat the silver nitrate to high temperatures in the presence of oxygen gas, you could convert the silver nitrate into silver oxide (Ag2O). This would be readily apparent if the reaction actually took place since silver nitrate is a while solid and silver oxide is a black solid.