What allows free oxygen atoms in ozone to react with other elements in the stratosphere?

The ability of free oxygen atoms in ozone to react with other elements in the stratosphere is primarily due to instability. Ozone, which consists of three oxygen atoms (O₃), is less stable than diatomic oxygen (O₂). This instability arises from the structure of the ozone molecule, which has a bent shape and possesses a high-energy arrangement of atoms. The individual atoms of oxygen in ozone can break apart more easily due to this unstable structure.

As a result of this instability, ozone can readily release its oxygen atoms, allowing them to engage in chemical reactions with other molecules, including pollutants and various atmospheric constituents. This reactivity is crucial for the roles ozone plays in both protecting the Earth from harmful ultraviolet (UV) radiation and participating in various chemical processes in the atmosphere.

In contrast, stability, while being a characteristic of many non-reactive substances, would imply that the ozone molecule does not easily break down or react. Density relates to the mass per unit volume of a substance and does not directly influence the chemical reactivity of ozone. Thus, instability is the key factor that enables the free oxygen atoms in ozone to interact with other elements within the stratosphere.