Learn Science - Oxygen and its chemistry

Oxygen is very abundant in the atmosphere and 89% of the seawater is oxygen only. Oxygen is essential for all animals and human beings. Plants use carbon from the carbon dioxide and leave oxygen out. That is how we are getting oxygen for our living free of cost. The chemistry of oxygen is discussed in this article.


Oxygen is a non-metallic element. This element belongs to Group VIa of the periodic table. Oxygen is essential for all living beings. It is a colourless, odourless, tasteless gas. Human beings take this oxygen for their living and leave it out as carbon dioxide. The plants take that carbon dioxide use carbon and leave oxygen out. Oxygen gas is fairly soluble in water. This is only making way for aerobic life in rivers, lakes and oceans.

Oxygen was discovered in the year 1772 by a Swedish chemist, Carl Wilhelm Scheele. An English chemist, Joseph Priestley, independently discovered oxygen in 1774 by the thermal decomposition of mercuric oxide. During 1775–80, French chemist Antoine-Laurent Lavoisier proposed the role of oxygen in respiration and also in combustion. He named it oxygen. In the Greek language, oxygen means acid former. He named it oxygen due to the acid formation tendency of this chemical when reacted with different other compounds.

46% of the mass of the earth crust is oxygen only. Oxygen is 21% by volume in the atmosphere. The seawater contains 89% of oxygen by weight. In nature, we get oxygen in many compounds which are formed by its reaction with metals and nonmetals.

Manufacturing method:

There are many methods prescribed, but we have to select the process based on the quantities required. In the laboratory, we can make oxygen by decomposition of compounds of oxygen like potassium chlorate and potassium nitrate. When the requirement is huge, though, these procedures are not viable as the cost involved is high. Mainly it will be manufactured using fractional distillation of liquid air. Air contains nitrogen, oxygen, and argon. Oxygen is having the highest boiling point of the other two and is hence is less volatile. Using this as an advantage, oxygen is separated from the air by fractional distillation.

Air is filtered for dust and water. The filtered air is compressed to 6.5 atm and cooled to -181^0C with the help of a reverse heat exchanger. The boiling point of oxygen at 1 atm is -183^0C. The boiling point of nitrogen at 1 atm is -195^0C. So when the air is compressed and cooled the oxygen liquefies first leaving the air in the gaseous stage. Argon has a similar boiling point to that of oxygen and argon also liquefies with the oxygen. This mixture is decompressed to near atmospheric pressure and again a low-pressure distillation is conducted. The oxygen obtained in the process is pure up to 99.5% oxygen.


The following are some of the important properties of this element
  1. The atomic number of oxygen is 8

  2. The atomic weight of the same is 15.9994

  3. The melting point is -218.4^0C

  4. The boiling point is -183 ^0C

  5. The is density at 1 at pressure and 0^0C temperature is 1.429g/l

  6. The naturally occurring oxygen will have three isotopes and they are oxygen-16 (99.759 percent), oxygen-17 (0.037 percent), and oxygen-18 (0.204 percent).

  7. There are two allotropic forms of oxygen known. They are oxygen O2 and O3(Ozone)


We all know how useful oxygen is for all of us. In addition to that oxygen is having many other industrial uses. Some of them are mentioned below
  1. The oxygen is mainly used in steel industry

  2. Many chemicals which are very useful for us in our day-to-day life are manufactured using oxygen. Acids like nitric acid and chemicals like hydrogen peroxide are manufactured using oxygen. These chemicals are very widely used in industry.

  3. Ethylene oxide is made using oxygen. This is used as an anti-freezing agent in the industry.

  4. Oxygen is used for making oxy acetylene which is used for welding and cutting metals.

  5. These days oxygen is widely used in treating industrial effluents and sewage


Oxygen is electronegative. So, this element is having a tendency of reacting with the majority of the elements and forms oxides. Almost all metals form oxides easily. Many metals get corroded on the surface of the metal by getting reacted with oxygen and forming a layer of metal oxide. In a wet atmosphere, oxygen will become more reactive. Many of the elements burn in presence of oxygen and water. Such reactive elements will be stored in a medium that is free from oxygen and moisture. The best example is sodium. When you expose sodium metal to the atmosphere it will start burning on its own. That is why many alkaline metals and alkaline earth metals are not available as metals in nature. We will get their oxides only and then we have to extract them from the oxides.

Some of the metals will be made to react with oxygen and a thin layer of oxide is formed on the surface of the metal. This will protect the inner core from getting reacted. This process is known as passivation.


Oxygen is one of the essential ingredients that is required for all living things in this universe. In addition to that oxygen plays a very important role in various industries. It is very essential for making steel which is very important in these modern days. Trees are the natural oxygen makers and give us oxygen at no cost. So, plant more trees and get oxygen freely to have a healthy life.


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