Final answer:
Among the given molecules or ions, only NO2- exhibits delocalized bonding due to its odd number of valence electrons and molecular orbital energy-level diagram.
Step-by-step explanation:
Delocalized bonding occurs when electrons are not localized between two specific atoms but are spread out over multiple atoms. In the given molecules or ions, NO2-, NH4+, and N3-, only NO2- exhibits delocalized bonding.
This is because NO2- has an odd number of valence electrons, and its bonding and properties cannot be explained by conventional theories such as the Lewis electron-pair approach or valence bond theory. The molecular orbital energy-level diagram for NO2 shows the presence of degenerate molecular orbitals, indicating delocalized bonding.