How does sodium react with oxygen in air?

Sodium is highly reactive with air, and its behavior depends significantly on the relative humidity and the physical state of the metal.1

In ordinary air, sodium reacts to form a film of sodium hydroxide, which can subsequently absorb carbon dioxide to form sodium bicarbonate. When exposed to dry air, the oxidation of sodium typically produces sodium monoxide (Na₂O).1

Sodium is significantly more reactive in its liquid state than as a solid, and it can ignite at approximately 125 °C (257 °F). In a relatively dry atmosphere, burning sodium emits a dense, caustic white smoke. Because sodium reacts with carbon dioxide, standard fire extinguishers are ineffective; specialized dry-powder extinguishers are required to manage these fires, which can reach temperatures exceeding 800 °C (1,500 °F). Due to this reactivity, sodium is typically stored in an inert atmosphere, such as nitrogen, or submerged in inert liquids like kerosene or naphtha.1