Radicals

The chemistry of the atmosphere is incredibly complicated (more detail here). Ozone is formed when an oxygen atom, which is an example of a radical, reacts with an oxygen molecule (O + O₂  ->  O₃).

CFC's contain chlorine, fluorine and carbon, an example is the compound CCl₃F which was used as an aerosol propellant. High up in the stratosphere, in the presence of UV radiation, the CCl₃F molecule can split apart to form a free chlorine atom (a free radical). Each Cl atom can then take part in a series of chain reactions which destroy ozone:

Cl +  O₃  ->  ClO  +   O₂

ClO  +  O  ->  Cl  +  O₂      and the chlorine radical goes on to destroy more ozone.

It is believed that every chlorine radical can destroy an average of 100,000 ozone molecules. it is worrying to think that we have put about 1,000,000 tonnes of CFC's into the atmosphere every year since the 1970's.

This is not required for GCSE!!! Back to atmosphere