Final answer:
CFCs and HCFCs have long atmospheric lifetimes, allowing them to reach the stratospheric ozone layer and contribute to its depletion. Their stability means they persist until UV radiation breaks them down, releasing chlorine atoms that destroy ozone molecules. International efforts like the Montreal Protocol have led to the phase-out of these substances.
Step-by-step explanation:
CFCs (Chlorofluorocarbons) and HCFCs (Hydrochlorofluorocarbons) have long atmospheric lifetimes, making them capable of reaching the stratospheric ozone layer. These compounds are made up of chlorine, fluorine, and carbon atoms and are known for their extreme stability, which allows them to slowly ascend into the stratosphere. The stability of CFCs means that they do not decompose in the lower atmosphere and can persist long enough to reach the stratosphere, where ultraviolet (UV) radiation breaks them down, releasing chlorine atoms. These chlorine atoms then catalyze the destruction of ozone (O3) molecules, leading to depletion of the ozone layer that protects Earth from harmful UV radiation.
Effective measures such as the Montreal Protocol on Substances that Deplete the Ozone Layer have been implemented to phase out the use of CFCs and related compounds. Alternatives like HFCs (Hydrofluorocarbons), which contain no chlorine or bromine, have been developed to replace CFCs and minimize ozone depletion. HCFCs, although still containing chlorine, are considered less harmful because they decompose more readily in the troposphere, reducing the number of ozone-destroying molecules that reach the stratosphere.