How do chlorofluorocarbons break down in the atmosphere?

Chlorofluorocarbons (CFCs) break down in the atmosphere when they are exposed to solar radiation, releasing chlorine atoms.

Chlorofluorocarbons, commonly known as CFCs, are a type of compound that was widely used in the 20th century in various applications such as refrigeration, air conditioning, and aerosol propellants. However, their stability and longevity in the atmosphere have led to significant environmental issues, most notably the depletion of the ozone layer. The process of CFC breakdown begins when they are released into the atmosphere.

CFCs are extremely stable and do not easily break down in the lower atmosphere. They can remain intact for decades or even centuries, slowly rising to the stratosphere, the second major layer of Earth's atmosphere. Once in the stratosphere, CFCs are broken down by solar radiation, specifically ultraviolet (UV) light. This process is known as photodissociation.

Photodissociation involves the absorption of a photon by a molecule, which provides enough energy to break the chemical bonds within the molecule. In the case of CFCs, the UV light breaks the bond between the carbon atom and one of the chlorine atoms. This releases a chlorine atom, which is capable of catalysing the destruction of ozone.

Each chlorine atom can catalyse the destruction of many thousands of ozone molecules before it is removed from the stratosphere. This is because the chlorine atom is not consumed in the reaction with ozone, but is instead recycled, allowing it to continue to catalyse further reactions. This process is what leads to the thinning of the ozone layer, commonly referred to as the 'ozone hole'.

In summary, the breakdown of CFCs in the atmosphere is a process that begins with their release into the atmosphere and ends with their photodissociation in the stratosphere. This process releases chlorine atoms, which are capable of catalysing the destruction of the ozone layer.