Chlorofluorocarbons CFCs are a class of compounds that contain carbon, chlorine, and fluorine atoms. They were widely used as refrigerants, propellants, and solvents in the past. However, it was discovered that CFCs have a detrimental impact on the ozone layer, which protects the Earth from harmful ultraviolet UV radiation.The ozone layer is primarily composed of ozone O3 molecules, which are formed by the reaction of oxygen O2 molecules with UV radiation. The ozone molecules absorb UV radiation, preventing most of it from reaching the Earth's surface. This process is essential for protecting living organisms from the harmful effects of UV radiation, such as skin cancer and cataracts.CFCs impact the ozone layer through a series of chemical reactions that occur when they are released into the atmosphere and exposed to UV radiation. The breakdown of CFCs in the ozone layer can be summarized in the following steps:1. Photodissociation: When CFCs are exposed to UV radiation, a chlorine atom is released from the molecule through a process called photodissociation. For example, in the case of CFC-12 CCl2F2 , the reaction is as follows: CCl2F2 + UV radiation CClF2 + Cl2. Ozone depletion: The released chlorine atom Cl reacts with an ozone O3 molecule, breaking it down into an oxygen molecule O2 and a chlorine monoxide ClO molecule: Cl + O3 ClO + O23. Regeneration of chlorine atoms: The chlorine monoxide ClO molecule reacts with another ozone O3 molecule, forming an oxygen molecule O2 and releasing a chlorine atom Cl : ClO + O3 Cl + 2 O2The released chlorine atom can then react with another ozone molecule, repeating the cycle and causing further depletion of the ozone layer. This process is known as the catalytic destruction of ozone, as a single chlorine atom can destroy thousands of ozone molecules before it is eventually removed from the stratosphere.To mitigate the harmful effects of CFCs on the ozone layer, the production and consumption of CFCs and other ozone-depleting substances have been phased out under the Montreal Protocol, an international treaty designed to protect the ozone layer. As a result, the ozone layer is gradually recovering, and it is expected to return to its pre-1980 levels by the middle of the 21st century.