Potassium reacts with air in different ways depending on the conditions, tarnishing rapidly at room temperature and forming potassium superoxide when burned.
Potassium is a highly reactive alkali metal. When exposed to air, it reacts readily.
Reaction with Air at Room Temperature
Immediately upon cutting, a fresh surface of potassium is bright and shiny. However, this shiny surface quickly changes appearance.
- Tarnishing: The surface of potassium soon tarnishes. This occurs because of its reaction with components found in the air.
- Oxygen: Potassium reacts with oxygen from the air.
- Moisture: Potassium also reacts with moisture (water vapor) from the air.
This reaction with oxygen and moisture causes the surface to lose its initial brightness.
Reaction with Air When Burned
When heated and ignited, potassium reacts vigorously with the air, producing a specific product.
- Burning in Air: If potassium is burned in air, the result is mainly formation of orange potassium superoxide, KO₂.
This is a more energetic reaction compared to the slow tarnishing process. The primary product formed under burning conditions is the superoxide.
In summary, potassium reacts with air both through a slow surface reaction with oxygen and moisture leading to tarnishing, and through a rapid reaction when burned, primarily forming orange potassium superoxide (KO₂).
