Properties of Oxygen and Ozone
Air to Breathe, Ozone Layer and Greenhouse Effect
The most abundant element in the earth's crust and essential for respiration, Oxygen also gives us the ozone layer to protect us from UV and is a Greenhouse gas
Element
Oxygen is an element. A single oxygen atom has eight electrons, eight neutrons and eight protons. It is very abundant in the earth’s crust, combined with other elements in different compounds. It also bonds to itself, and this is what we are concerned with in this article.
Allotropes
When an element can bond to itself in more than one way, the different forms of that element are called “allotropes”. So in another article you can read about the different allotropes of carbon. The most common and stable allotrope of oxygen is di-oxygen or oxygen gas. We are all aware of the importance of oxygen gas, without it there would be no life on planet earth! The other major allotrope, which is much less stable, is also very important to life on earth. This allotrope is called tri-oxygen or ozone.
The Air we Breathe
Oxygen gas makes up about one fifth of the atmosphere of the earth. Most of the rest of the atmosphere is nitrogen gas. It is oxygen that our bodies absorb into the bloodstream through the lungs and is used in the muscles to move and do work.
Protection
Ozone is a different matter entirely. There is very little ozone in the earth’s atmosphere and it is very unstable and reactive. It’s presence in the atmosphere, however, is either very important or harmful, depending on where it is. In the stratosphere, between 10km and 50km above the earth’s surface it forms the Ozone Layer. This is an important protective layer which filters out most of the high energy Ultra-Violet radiation from the sun which would damage much of the life on earth. The ozone layer is thin and has been depleted recently by the release of Chloro-Fluoro-Carbons (CFCs) and other similar chemicals which cause ozone to break down and become oxygen gas.
Pollutant
When ozone is present at ground level and in the troposphere (10-18 km above earth’s surface) it is considered a pollutant and a greenhouse gas. At ground level ozone is formed by the reaction of sunlight with hydrocarbons and nitrogen oxide gases from vehicle and industrial emissions. On a sunny day in a busy city the levels of photochemical smog containing ozone can be high. This smog can cause asthma and other lung conditions.
Greenhouse Effect
The ozone caused by the action of sunlight on pollutants can also rise to the troposphere and join carbon dioxide and other polluting gases that create the Greenhouse Effect. These gases act as a kind of blanket around the earth, trapping infrared radiation emitted by the earth and causing temperatures to rise.
Other Uses
Finally ozone is used both industrially and commercially due mainly to its reactivity. It is used as a clean way of purifying water both in industry and in the home in hot-tubs and fish tanks. It is also used to disinfect laundry both in hospitals and in the home.
A paradoxical element indeed! It both gives and protects life, while it is also capable of destroying it. How careful we must be!
