Answer:
NO3 that is the answer to the question
Heating an atom excites its electrons and they jump to higher energy levels. When the electrons return to lower energy levels, they emit energy in the form of light. ... Every element has a different number of electrons and a different set of energy levels. Thus, each element emits its own set of colours.
Phosphorous has 5 valence electrons and so gaining 3 electrons will make it isoelectronic with the stable noble gas argon, and will produce the P3- ion