CFCs are highly stable, nonflammable, and nontoxic liquids or gases at room temperature. These properties made them very popular for home and industrial applications. However, their extreme chemical stability created a major environmental problem.
Since CFCs do not react easily, they do not break down in the lower atmosphere. Instead, they slowly drift up into the stratosphere over many decades. Once there, intense ultraviolet light from the sun strikes the CFC molecules.
This high-energy radiation breaks the relatively weak bond between carbon and chlorine. This split releases a highly reactive chlorine atom called a free radical. The active chlorine radical attacks ozone molecules and converts them into oxygen gas.
A single chlorine radical can destroy thousands of ozone molecules through a chain reaction. This continuous destruction thins the ozone layer that protects Earth from ultraviolet rays. Many students confuse the thinning of the ozone layer with global warming.
Although both issues involve the atmosphere, they are two separate environmental challenges. The Montreal Protocol successfully phased out these harmful chemicals to protect our planet.