Final answer:
CFC molecules break down in the upper atmosphere due to ultraviolet (UV) radiation, releasing chlorine atoms that destroy ozone molecules.
Step-by-step explanation:
The CFC molecule breaks down once it reaches the upper atmosphere primarily due to ultraviolet (UV) radiation. This radiation dissociates the CFC molecules, releasing highly reactive chlorine (Cl) atoms. These chlorine atoms catalyze the destruction of the ozone layer, which leads to an increase in harmful UV radiation reaching the Earth's surface.
For example, the reaction of CFC-13 with a photon of light can be described as:
CFC13 + hv → CFC12 + Cl.
This photochemical process is critical to understanding both the depletion of the ozone layer and the global efforts to replace CFCs with compounds that have less impact on the stratospheric ozone.