State two forms in which the elemental oxygen is found in the earth s atmosphere Mention in brief the - Science - Atoms and Molecules

Question

State two forms in which the elemental oxygen is found in the
earth’s atmosphere Mention in brief the essential function
performed by each at the place they are found What are CFCs and why
are these considered harmful for the life on the earth?

Akanksha · Accepted Answer

Elemental oxygen is found in the earth’s atmosphere are
oxygen, 
O2,
and ozone, 
O3

Ozone is present as a thin layer in a region of Earth’s
stratosphere

The Ozone shield protects the earth from much of the sun's harmful
radiation as it absorbs the medium frequency ultraviolet light The
UV light saves us from diseases like skin cancer The defensive role
of the ozone layer is so vital that scientists believe life on land
most likely would not have evolved

Oxygen is present in the troposphere, the layer of atmosphere
closest to the earth Oxygen is one of the most important elements
required to sustain life Generation and maintenance of all our life
processes are regulated by oxygen

Chlorofluorocarbons are also known as CFCs They are used in
refrigerators, air conditioners, and aerosol sprays CFCs are
responsible for damaging the ozone layer and have led to the
formation of the ozone hole in the atmosphere A rapidly depleting
ozone layer allows the harmful UV radiations of the sun to reach
the Earth, which is responsible for an increase in the cases of
skin cancers in humans
The
Cl atoms of chlorofluoro carbons can destroy ozone molecules
through a variety of catalytic cycles In the simplest example of
such a cycle, a chlorine atom reacts with an ozone molecule, taking
an oxygen atom with it (forming ClO) and leaving a normal oxygen
molecule The chlorine monoxide (i e , the ClO) can react with a
second molecule of ozone (i e , O3) to yield another
chlorine atom and two molecules of oxygen The chemical shorthand
for these gas-phase reactions is:
Cl
+ O3 → ClO + O2 – The chlorine
atom changes an ozone molecule to ordinary oxygen
ClO
+ O3 → Cl + 2O2 – The ClO from the
previous reaction destroys a second ozone molecule and recreates
the original chlorine atom, which can repeat the first reaction and
continue to destroy ozone
The
overall effect is a decrease in the amount of ozone

State two forms in which the elemental oxygen is found in the earth’s atmosphere. Mention in brief the essential function performed by each at the place they are found. What are CFCs and why are these considered harmful for the life on the earth?