How is ozone formed naturally in the stratosphere?

Ozone is naturally formed in the stratosphere through a process called the ozone-oxygen cycle.

The ozone-oxygen cycle, also known as the Chapman cycle, is a series of chemical reactions that occur in the stratosphere and result in the creation and destruction of ozone. This cycle is crucial for life on Earth as it creates the ozone layer, which protects us from the Sun's harmful ultraviolet (UV) radiation.

The process begins with the dissociation of molecular oxygen (O2) by solar UV radiation. This high-energy radiation breaks the bonds between the two oxygen atoms, creating individual oxygen atoms (O). These free oxygen atoms can then react with other oxygen molecules to form ozone (O3). This reaction is exothermic, meaning it releases energy, which helps to warm the stratosphere.

However, the ozone isn't stable and can be easily broken down. It can absorb UV radiation, which causes it to dissociate into molecular oxygen and a free oxygen atom. This is a crucial part of the cycle as it is this absorption of UV radiation that protects us from its harmful effects. The free oxygen atom can then go on to react with another oxygen molecule to form more ozone, and the cycle continues.

It's important to note that while this cycle naturally creates and destroys ozone, human activities can disrupt it. Certain pollutants, such as chlorofluorocarbons (CFCs), can catalyse the breakdown of ozone, leading to the depletion of the ozone layer. This is a significant environmental issue as it can increase the amount of harmful UV radiation that reaches the Earth's surface, with potential impacts on human health and ecosystems.

In summary, ozone is naturally formed in the stratosphere through the ozone-oxygen cycle. This involves the creation of ozone from oxygen molecules and free oxygen atoms, and its subsequent breakdown, a process that both creates the ozone layer and protects us from UV radiation.