We have discovered a new type of reaction for atmospheric Na species and propose that this type of reaction will dominate its chemistry. The third order rate constants for NaO + O2+ M and NaO + CO2+ M were measured at 297 K in a flow tube study. The rate constants for NaO + O2with He, N2, and N2O as third bodies are (1.3±0.8), (3.5±0.7), and (11±4)×10−30cm6molecule−2s−1. The rate constants for NaO + CO2with N2and N2O as third bodies are (8.7±2.6) and (12±5)×10−28cm6molecule−2s−1. We show that these association reactions, and others like them, will produce Na compounds that are likely to render Na species inactive in stratospheric ozone chemistry. The reactivities of NaO, NaO2, NaO3, and NaCO3with O atom