Open In App

Dioxygen – Definition, Properties, Preparation, Uses

Last Updated : 01 Apr, 2022
Like Article

Oxygen is a member of the periodic table’s chalcogen group, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements and other compounds. Oxygen is the most abundant element on Earth, and it is the third-most abundant element in the universe after hydrogen and helium. Diatomic oxygen gas now accounts for 20.95% of the Earth’s atmosphere. Oxygen, in the form of oxides, accounts for nearly half of the Earth’s crust.

The chemical element with the symbol O and atomic number 8 is oxygen. 


One of the most common allotropes of elemental oxygen is dioxygen, which has the chemical formula O2. It is commonly referred to as oxygen, but to distinguish it from elemental oxygen, it is also referred to as dioxygen, molecular oxygen, or oxygen gas. 

With the exception of noble gases, oxygen gas reacts with almost all elements. The resulting compound is referred to as oxides. Even though it is not flammable on its own, oxygen gas is critical for combustion. It is also a life-giving gas because mammals require oxygen to survive and it aids in the release of energy.

Physical Properties of Dioxygen

  1. It’s a gas with no odour, colour, or taste.
  2. With a density of 1.429 g/L, it is heavier than air.
  3. It is slightly soluble in water, just enough to support aquatic life.
  4. The melting point of oxygen is approximately 54.36 K, and the boiling point is approximately 90.188 K.
  5. Depending on the temperature and pressure, oxygen can exist in all three states: solid, liquid, and gas.

Chemical Properties of Dioxygen

  • It reacts directly with almost all metals and nonmetals to form oxides of the elements involved.

4Na + O2 → 2Na2O (With Metal)

C + O2 → CO2 (With Non-metal)    

  • It has a paramagnetic nature.
  • Normally, oxygen does not react with acids and bases.
  • Because oxygen is a good oxidant, it aids in combustion.

Fuel + O2 ⟶ CO2 + H2O

  • The formation of rust on iron is caused by the combination of oxygen and moisture.

Fe  + O2 + H2O  ⟶ Fe2O3.nH2O (Hydrated Iron Oxide)

Laboratory Preparation of Dioxygen

In the laboratory, dioxygen can be prepared in a variety of ways.

  • The catalytic decomposition of Sodium Potassium Chlorate with Magnesium dioxide yields dioxygen. This reaction takes place when heated in the presence of MnO2 at 420K.

2KClO3  →  2KCl + 3O2  

  • The thermal breakdown of metal oxides with low electrode potential in the electrochemical series, such as Mercury and Silver oxides, produces dioxygen.

2HgO (s) → 2Hg (l) + O2 (g)

2PbO2 (s) → 2PbO (s) + O2 (g)

  • When oxygen-rich salts, such as nitrates and permanganates, are thermally decomposed, Dioxygen is produced.

2KNO3 →  2KNO2+ O2

2KMnO4 → K2MnO4  + MnO2 + O2

2NaNO3  → 2NaNO2  + O2

  • The decomposition of Hydrogen Peroxide also produces oxygen, and manganese(IV) oxide is used as a catalyst to speed up the decomposition.

2H2O2(aq) → 2H2O(l) + O2(g)

Industrial Production of Oxygen

There are two primary methods for industrially producing dioxygen from the air.

  1. N2 distils as a vapour while O2 remains as a liquid in a fractional distillation of liquefied air. In this case, liquid air is a mix of liquid Nitrogen and liquid Oxygen. Because of its lower boiling point, nitrogen is more volatile. It boils first, leaving only pure oxygen behind.
  2. Another method involves passing clean, dry air through one bed of a pair of zeolite molecular sieves, which absorbs the N2 gas and delivers the gas, which is 90-93% oxygen.

Uses of Dioxygen

  • Dioxygen is required for respiration.
  • It is found in oxygen cylinders used in hospitals and mountaineering.
  • In the form of oxy-acetylene, it is used for welding and cutting metals.
  • When oxygen gas reacts with acetylene gas, an oxy-acetylene flame is formed, which is used for cutting and welding metals.
  • It is used in liquid rocket fuel.
  • It is used in the synthesis of nitric acid.
  • It is used in artificial respiration in conjunction with carbon dioxide or methane.
  • Laser cutting makes use of oxygen.
  • In combustion processes, oxygen is used. Materials that do not normally burn in air burn easily in oxygen, so combining oxygen and air improves combustion.
  • Oxygen is used in water treatment processes such as wastewater purification and sewage treatment.

Sample Questions

Question 1: Why is dioxygen a gas but sulphur a solid? 


The O—O bond is weaker than the S—S bond due to greater inter-electronic repulsions in small oxygen atoms; additionally, because oxygen is smaller and more electronegative, it forms p-p multiple bonds. As a result, it exists as O2 molecules held together by a weak van der Waals force. At room temperature, oxygen exists as a gas. Sulphur has a lower proclivity to form p-p multiple bonds. Furthermore, it has a large atomic size, low electronegativity, and forms strong S—S single bonds, which explains why it has higher catenation and exists as S8 molecules with a puckered ring structure. As a result, at room temperature, sulphur is a solid.

Question 2: Does Oxygen react with Alkali Metals?


Oxygen has a high reactivity with alkali metals (Group I elements). Alkali metals should be kept away from oxygen to avoid being oxidised. Metals at the bottom of the group are more reactive than those at the top.

Question 3: What is the use of dioxygen?


Dioxygen is required for respiration. It is found in oxygen cylinders used in hospitals and mountaineering. In the form of oxy-acetylene, it is used for welding and cutting metals.

Question 4: Is dioxygen considered a molecule or a compound?


It is a diatomic molecule made up of two oxygen atoms joined by a covalent bond.

Question 5: Dioxygen is a blue-coloured gas and is very essential for life. True or false?


The oxygen we breathe is in the form of a diatomic molecule known as dioxygen gas. It is a gas that is colourless, odourless, and tasteless. It is required for life’s sustenance because plants and animals use it in the process of respiration, which breaks down food molecules to produce energy. As a result, the given statement is false.

Previous Article
Next Article

Similar Reads

What is Sodium Chloride? - Definition, Preparation, Properties, Uses
Salt's chemical name is sodium chloride. Sodium is an electrolyte that regulates your body's water content. Sodium is also involved in nerve impulses and muscle contractions. Sodium chloride is a medication used to treat or prevent sodium loss caused by dehydration, excessive sweating, or other factors. What is Sodium Chloride (or Common Salt)? It
6 min read
Dinitrogen - Definition, Preparation, Properties, Uses
Nitrogen is the lightest element in Periodic Table Group 15, also known as the pnictogens. Dinitrogen, a colourless and odourless diatomic gas with the formula N2, is formed when two atoms of the element join together at STP. Dinitrogen is the most abundant uncombined element, accounting for around 78% of the Earth's atmosphere. Nitrogen is found i
6 min read
Hydrogen Chloride - Definition, Preparation, Properties, Uses
As a hydrogen halide, the compound hydrogen chloride has the chemical formula HCl. It is a colourless gas at ambient temperature that emits white fumes of hydrochloric acid when it comes into contact with air-water vapour. In technology and industry, hydrogen chloride gas and hydrochloric acid are critical. Hydrochloric acid, an aqueous solution of
7 min read
Properties of Acids - Definition, Examples, Properties, Uses
Acids have a corrosive effect. When we cook acidic foods in brass or copper utensils, the metal reacts and corrodes. When copper reacts with acid, it creates copper salt. Copper salts are toxic and taint the flavour of cooked food. This is why we don't keep liquid foods in metallic containers. Tea should also be served in copper mugs. Tin, a brilli
6 min read
Ammonia - Properties, Preparation, Uses, Effects
Ammonia is made up of hydrogen and nitrogen. It is known as ammonium hydroxide in its aqueous form. This inorganic compound has a strong odour. It is dangerous and caustic in its concentrated form. Ammonia has a density of 0.769 kg/m3 at STP, making it lighter than air. It's commonly used as a fertiliser. It's also used in the production of explosi
6 min read
Ozone - Preparation, Properties, Uses, Effects
Ozone is too reactive to stay in the atmosphere at sea level for long. It is formed from atmospheric oxygen in the presence of sunlight at a height of about 20 kilometres. This ozone layer shields the earth's surface from an excess of ultraviolet (UV) radiation. It is an unstable, blue, diamagnetic gas with a distinctive pungent odour that shields
7 min read
Ozone - Properties, Structure, Preparation, Reactions and Uses
Ozone is an irritating light blue gas that, even at low concentrations, is explosive and poisonous. It naturally occurs in small levels in the Earth's stratosphere, where it absorbs solar UV light, which would otherwise cause severe harm to living things on the Earth's surface. Under some conditions, photochemical reactions in the lower atmosphere
8 min read
Sulphur Dioxide - Structure, Preparation, Properties, Uses
The p-block, which spans groups 13 to 18, is located on the right side of the normal periodic table. Their electrical configuration is ns2 np1–6 in general. Despite being the first element in group 18, helium is not part of the p-block. Except for the first row, each row in the table has six p-elements. The only block with all three categories of e
8 min read
Phosphine - Structure, Preparation, Properties, Uses
The final electron of a P block element enters one of the three p-orbitals of the shell in which it is found. There are six groups of p-block elements since a p-subshell has three degenerate p-orbitals, each of which may hold two electrons. Because of their tendency to lose an electron, P block elements are lustrous and typically strong conductors
5 min read
Ammonia |Structure, Properties, Preparation, Uses
Ammonia (NH₃) is a colorless gas with a sharp, pungent odor. It is a compound of nitrogen and hydrogen and plays a crucial role in both the industrial sector and biological processes. Let's learn about ammonia in detail, including its structure, properties and uses. AmmoniaAmmonia is nitrogen and hydrogen-based chemical. It is made up of one nitrog
7 min read