Nitrogen and sulfur

Nitrogen, sulfur and pollution

Nitrogen is unreactive because of its strong N≡N triple bond (945 kJ mol⁻¹) and lack of polarity. Ammonia is a weak base: $\mathrm{NH_3+H^+\rightarrow NH_4^+}$ (dative bond, tetrahedral ion). Warming an ammonium salt with alkali releases NH₃. Oxides of nitrogen form in lightning and hot engines ($\mathrm{N_2+O_2\rightarrow2NO}$); catalytic converters remove them ($\mathrm{2CO+2NO\rightarrow2CO_2+N_2}$). NO₂ catalyses the oxidation of SO₂ in the atmosphere: $\mathrm{SO_2+NO_2\rightarrow SO_3+NO}$, $\mathrm{NO+\frac12O_2\rightarrow NO_2}$, contributing to acid rain. NOₓ and hydrocarbons in sunlight form photochemical smog (including PAN).