Page 1 - 2. Lesson notes- Bio- geo chemical cycles-2

SAI International School
Subject- Biology
Chapter- Natural Resources
Subtopic- Bio- geo chemical cycles-2
Module- 35
Lesson Notes

OZONE

Ozone, or trioxygen, is an inorganic molecule with the chemical formula O ₃.
It differs from normal oxygen (O2) in having three atoms in its molecule (O3).

Role of Ozone in the atmosphere:
Ozone is a gas in the atmosphere that protects everything living on the Earth from harmful

ultraviolet (UV) rays from the Sun.

Ozone layer depletion:
Scientists discovered a “hole” in the ozone layer over the Antarctic in the 1980s.

Ozone layer depletion is the thinning of the ozone layer present in the atmosphere.
This happens when the chlorine and bromine atoms in the atmosphere come in contact with

ozone and destroy the ozone molecules.

Ozone depletion occurs when chlorofluorocarbons (CFC) and halon—gases formerly found in
aerosol spray cans and refrigerants—are released into the atmosphere.

CFC's and halon cause chemical reactions that break down ozone molecules, reducing
ozone's ultraviolet radiation-absorbing capacity.

Ozone-Depleting Substances Sources

Chlorofluorocarbons (CFC's) Refrigerators, air-conditioners, solvents, dry-cleaning

agents, etc.
Halon Fire-extinguishers

Carbon tetra chloride Fire extinguishers, solvents

Methyl chloroform Adhesives, aerosols
Hydro fluorocarbons Solvent cleaning, fire extinguishers, solvent cleaning

Effects Of Ozone Layer Depletion

The depletion of the ozone layer has harmful effects on the environment.