Environmental Context. N₂O₅ is an important nitrogen reservoir in polar stratospheric clouds found in Antarctica and involved with the ozone hole. Here we provide valence bond representations for the gas-phase formation and decomposition of this molecule.

Abstract. Qualitative valence bond considerations are used to suggest how electronic reorganization could proceed for (a) the formation of N₂O₅ via the reactions NO₂ + O₃ → NO₃ + O₂, and NO₂ + NO₃ → N₂O₅, and (b) the thermal decomposition of N₂O₅ via the following sets of reactions: (i) N₂O₅ → NO₂ + NO₃, 2NO₃ → O₂NOONO₂ →2NO₂ + O₂; (ii) NO₂ + NO₃ → ONOONO₂ → NO + O₂ + NO₂, NO + NO₃ → 2NO₂. Increased-valence structures, which possess one-electron bonds and fractional electron-pair bonds as well as ‘normal’ electron-pair bonds, are used to represent the electronic structures of the molecules.