What is oxygen and its atomic mass? | properties of oxygen

What is oxygen? Live animals can live for some time without food and water, but without oxygen, it is difficult to survive for a few minutes. Humans get energy from food with the help of respiration and oxygen plays a very important role in this process.

The upper layer of the Earth has 45% oxygen and without oxygen, the compound cannot maintain its hardness. If oxygen disappears from the Earth even for 5 seconds, it is difficult to imagine what will happen here.

What is Oxygen

In this article, we will learn about what is oxygen as well as its molecular formula and properties. So first of all, let's know what is oxygen?

What is oxygen?

Oxygen is a chemical element with its symbol (O) and atomic number 8. It is a member of the Halogen group in the periodic table. Besides being highly reactive nonmetal, it is also an oxidizing agent that readily forms oxides with other compounds with most elements.

It is the third most abundant element in the universe, after hydrogen and helium on a mass basis. At standard temperature and pressure, the element's two atoms form Di-oxygen with O2 to form a colorless and odorless diatomic gas. The diatomic oxygen gas is 20.95% of the Earth's atmosphere. It makes up about half of the Earth's crust in the form of oxides.

Dioxygen provides the energy released in combustion and aerobic cellular respiration, and many major classes of organic molecules in living organisms contain oxygen atoms, such as proteins, nucleic acids, carbohydrates, and fats.

Most of the mass of organisms living as a component of water is oxygen, which is the major component of life. Oxygen in the Earth's atmosphere is continuously replenished by photosynthesis, which uses the energy of sunlight to produce oxygen from water and carbon dioxide.

Oxygen is very chemically reactive in order to remain a free element in the air without being constantly assigned by the photosynthetic action of living organisms. Oxygen, another form of ozone (O3) (allotrope), strongly absorbs ultraviolet UVB radiation and the high-altitude ozone layer helps protect the biofire from ultraviolet radiation. However, ozone present on the surface is a byproduct of smog and thus a pollutant.

What is the atomic mass of oxygen?

The atomic mass of oxygen is 15.999 AMU. The complete form of AMU is the atomic mass unit.


Oxygen was isolated by Michael Sendivogius before 1604, but it is generally believed that the element was discovered independently by Carl Wilhelm Scheele in the laboratory in 1773 or earlier, and in 1774 by Joseph Priestley in Wiltshire.

Priority is often given to Priestley since his work was first published. However, Priestley called oxygen " dephlogisticated air", and did not recognize it as a chemical element. The name oxygen was coined in 1777 by Antoine Lavoisier, who first recognized oxygen as a chemical element and correctly portrayed the role it played in combustion.

Common uses of oxygen include steel, plastic and textile production, brazing, welding and harvesting of steels and other metals, rocket propellant, oxygen therapy, and life support systems in aircraft, submarines, spaceflight, and diving.

Physical properties of oxygen

Oxygen dissolves more easily in water than nitrogen and in freshwater more easily than in seawater. About 1 molecule is dissolved for every 2 molecules of N2 (1: 2) compared to an atmospheric ratio of about 1: 4 in water in equilibrium with air.

The solubility of oxygen in water is temperature dependent, and dissolves more than 20 ° C at about 0 ° C twice. At 25 ° C of air and 1 standard atmosphere (101.3 kPa), freshwater contains about 6.04 mL (mL) of oxygen per liter and seawater contains about 4.95 mL per liter.

At 5 ° C the solubility increases by 9.0 mL (more than 50% at 25 ° C) per liter of water and 7.2 mL (45% more) per liter for seawater.

Chemical properties of oxygen

At standard temperature and pressure (STP), the element's two atoms bind with the formula O2 to form dioxins, a colorless, odorless, tasteless diatomic gas. Oxygen is a member of the halogen group on the periodic table and is a highly reactive nonmetal element. As such, it easily forms compounds (especially, oxides) with almost all other elements.

Oxygen is a strong oxidizing agent and has the second-highest electronegativity of all reactive elements, second only to fluorine. By mass, oxygen is the third most abundant element in the universe after hydrogen and helium and is the most abundant element in the Earth's crust by mass, which is about half of the mass of the crust.

Free oxygen is chemically reactive without the photosynthetic action of living beings appearing on Earth, who use the energy of sunlight to produce elemental oxygen from water. Elemental O2 began to accumulate in the atmosphere after the evolutionary form of photosynthetic organisms about 2.5 billion years ago. Diatomic oxygen gas is currently 20.8 percent of the volume of air.

How to make oxygen in the laboratory

A)     Using heat

Oxygen gas can be made in the laboratory by heating potassium permanganate (KMnO4) or potassium chlorate (KClO3) dust. For this, potassium permanganate or potassium chlorate dust is placed in a rigid test tube and heated to about 360-370 C.

In this experiment, when manganese dioxide (MnO2) is used as a catalyst, oxygen gas is released by heating it to about 240-2500 C.

Chemical reaction:


2KClO3 (s)   →     2KCl (s) + 3O2 (g)

B)     Without the use of heat

Oxygen gas in the laboratory can also, be obtained from hydrogen peroxide without the use of heat.

In this experiment, manganese dioxide is placed in a conical flask and hydrogen peroxide is slowly poured over it with the help of a funnel.

The oxygen produced in this process is stored in the gas tank by displacing water with the help of a delivery tube. Manganese dioxide (MnO2) is worked as a catalyst in this process.

Chemical reaction:


2H2O2 (aq)   →     2H2O (l) + O2 (g)

Use of oxygen gas

Oxygen is used in the respiratory process. During respiration, oxygen enters the body of the animal and gives energy to the animal by reacting with the carbohydrates in the food. This is the power by which living beings survive.

  • It is used in the respiratory process. During respiration, oxygen enters the body of the animal and gives energy to the animal by reacting with the carbohydrates in the food. This is the power by which living beings survive.
  • It is used to produce sulfuric acid, chlorine, etc.
  • Oxygen gas is used in welding because it reacts with hydrogen to produce high temperatures.
  • Liquid oxygen is used as fuel in missiles and rockets.
  • O2 is filled into a cylinder and used for respiration.

Conclusion: Oxygen is the vital air. Without it, living beings cannot survive even a few minutes.

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