Natural+Ozone+Formation+and+Destruction

A thin layer of ozone gas (O3) encircles the Earth and prevents about 99% of the ultraviolet light (UV) from the sun from reaching the Earth. It occurs in the stratosphere between 12 and 50 km above the Earth.

The ozone is formed when the double bond in an oxygen molecule is broken due to high energy UV light from the sun.

This causes an oxygen free radical. A very reactive oxygen atom (with two single unpaired elcetrons.) O2 (g) ---> 2O* (g)

This oxygen free radical then reacts with another oxygen molecule to give an ozone molecule. O*(g) + O2--->O3 (g)

This process is visually shown in the diagram below.



The ozone molecule has a strange structure so that it's bonds are between single and double. This allows for this molecule to easily break up by absorbing more UV light. O3(g)->O* (g) + O2(g) O* (g) + O3(g)>O2(g)

Since the formation and natural destruction of ozone are opposite and at equal rates then the amount of natural ozone should stay constant. This is called a stasis state. Both processes remove harmful UV rays from the sun.