Electrophilic Aromatic Substitution

Nitration of benzene is a classic electrophilic aromatic substitution in which a strong electrophile attacks the delocalized pi system of the ring. Concentrated sulphuric acid protonates nitric acid, which then loses water to generate the nitronium ion: $HN{O}_3+2H_{2}S{O}_4\to N{O}_2^{+}+H_3{O}^{+}+2HS{O}_4^{-}$. This linear nitronium ion is the effective electrophile that adds to benzene to form a resonance-stabilized arenium ion (sigma complex), which then loses a proton to restore aromaticity and yield nitrobenzene. The nitrosonium ion $N{O}^{+}$ forms in nitrosation reactions with nitrous acid, not in nitration, so it is wrong. The nitrate ion $N{O}_3^{-}$ is negatively charged and cannot act as an electrophile toward an electron-rich ring, so it is incorrect. The $N{O}_2^{\bullet }$ radical belongs to radical chemistry, not to this ionic substitution, so it does not apply. The overall reaction preserves aromaticity because, unlike addition, substitution allows the ring to regain its fully delocalised sextet of pi electrons after the proton is lost from the sigma complex. This explains why benzene undergoes substitution rather than addition despite being formally unsaturated. This is precisely the NCERT mechanism for aromatic nitration. A plausibility check: only a positively charged species can be attracted to the electron-rich benzene ring, confirming the nitronium ion.