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Oxygen Definition, Elements Information and Properties

Nov 8, 2022

The oxygen molecule model is a chemical element- a compound that contains only one kind of atom, oxygen. The atomic number of the molecular form of oxygen is 8, represented by the chemical symbol O. The nucleus of an oxygen atom consists of eight protons. Oxygen is in its gaseous state at room temperature with no odour, colour, or smell. In nature, oxygen exists as a molecule. Two oxygen molecules must make a covalent double bond to create oxygen or O2. Oxygen is crucial for maintaining human life.

Molecule of Oxygen


Typically, oxygen exists as a molecule. It is known as dioxygen, a molecular form of oxygen.

Molecular Formula of Oxygen

When a substance exists in more than two distinct forms, it is said to allotrope. Because oxygen may exist in three different forms, it is an allotrope. The first is referred to as atomic or elemental oxygen and is denoted by the molecular formula O. The molecular formula for the second form of oxygen, also known as molecular oxygen or dioxygen, is O2. Ozone is the final and third form of oxygen, symbolised by the molecular formula O3.

Types of Oxygen

Elemental Oxygen, O

Atomic or elemental oxygen, or O, is rarely found on earth. It is because its outermost shell only contains 6 electrons. Elemental oxygen looks for bonds with other elements to fill its outer shells with 8 electrons. Since elemental oxygen is very reactive, the atmosphere does not contain substantial concentrations.


The oxygen molecule structure of O is O – O.

Molecular Oxygen, O2: Dioxygen

The word dioxygen is derived from the Greek word di, which means twice. This type of oxygen is produced when two oxygen atoms share two valence electrons, making it less reactive than elemental oxygen.


Dioxygen is the most prevalent type of oxygen on earth and has the chemical formula O2. The atmosphere and oceans both contain this type of oxygen, which is also called molecular oxygen. The dioxygen molecule is created by the chemical bonding of two oxygen molecules. Because each atom’s outer electron shell shares two pairs of electrons, their bond is double covalent. 

During the past 2.4 billion years, dioxygen has been essential for the survival and evolution of many creatures. This type of oxygen is inhaled by all animals, including humans, to aid in cellular energy production. Anaerobic bacteria are one type of creature that can survive without oxygen. Even though life may have originated in an anaerobic environment, many living organisms today depend on oxygen for survival.


This type of double bond is known as a covalent bond since each electron is shared rather than transferred to another atom. After nitrogen gas, dioxygen is the second most common gas in the atmosphere. Dioxygen has no colour or smell.

The oxygen molecule structure of O2 is O = O.


Ozone, O3

Ozone, or O3, is the third form of oxygen molecule structure. Despite being colourless, ozone does have a smell. The name ‘ozone’ has evolved from the Greek word ozein, which signifies smell. In thunderstorms, lightning breaks up the air’s molecular oxygen. These single oxygen molecules combine with other dioxygen molecules present in the air to create ozone, O3. This newly created ozone can be smelled when it travels to the earth’s troposphere as the airflow from the thunderstorm. Animals use this sweet-smelling aroma to recognise and predict the arrival of rain easily. But ozone is frequently found in the stratosphere of the planet.

O2 molecules are broken up into individual oxygen molecules by ultraviolet (UV) light. The single oxygen molecule attaches to O2 molecules (the chemical formula of dioxygen) to form O3, ozone molecules. Since more UV radiations are present in the earth’s stratosphere layer, it comprises higher ozone concentrations. Because the ozone layer blocks UV light, fewer O2 molecules may split near the earth’s lower atmosphere (troposphere layer). However, ozone can still be formed in the troposphere layer when O2 is subjected to intense heat and pressure.


The oxygen molecule structure of O3 is O ☰ O

Did You Know?


Car engines can also produce ozone, a pollutant. Therefore, modern cars have catalytic converters to turn O3 back into O2.


There is oxygen all around us!

  • After hydrogen and helium, the O2 molecule is the third most prevalent element in the universe.
  • The oxygen molecule is the most common element on the earth’s crust in terms of its mass. Sand and minerals like quartz are created when O2 molecules combine with silicon and other atoms to form compounds.
  • In the atmosphere, it ranks as the second-most prevalent gas. The concentration of oxygen in the air is about 21%. 
  • Oxygen is a highly reactive gas. It blends seamlessly with other components. Plants and other aquatic organisms use it to create their food.
  • Additionally, oxygen makes up the bulk of the oceans on earth. Two hydrogen atoms and one oxygen atom make up the structure of the water molecule (H2O). Water contains more hydrogen atoms, although hydrogen has a lower mass in water. Nearly 90% of the mass of water is made up of oxygen.
  • Since human bodies are made up of 70% water, it is the most prevalent element (by mass) in the human body.

Liquid Oxygen and Solid Oxygen

When a molecule for oxygen condenses to -183°C, it converts into liquid. Liquid oxygen is also utilised as fuel for rockets. Oxygen gets solid when the temperature falls below -218.79°C. The O2 molecule is transparent and has a pale sky-blue colour in its liquid and solid forms. 

Interesting Fact:

The oxygen molecule model is generally in its liquid form in a physical state. It has numerous industrial and medical applications.

O2 Molecule: Source for Life!

The molecular form of oxygen, O2, is essential for life. All living organisms use oxygen for cellular respiration, the process through which cells obtain energy. Both human beings and other terrestrial animals inhale oxygen into the lungs as part of the air. The oxygen from the lungs goes into the bloodstream and flows into each cell of the human body. Aquatic animals use gills to absorb oxygen dissolved in the water. Similarly, insects use small external pores called spiracles, which lead into the network of tubes known as the trachea.

Plants use a molecular form of oxygen, the O2 molecule, for cellular respiration. When plants perform the process of photosynthesis, they take in carbon dioxide from the atmosphere and release back oxygen. In dim lights, the rate of photosynthesis is lower than the rate of respiration. While in sunlight, photosynthesis outpaces respiration and produces more oxygen than it consumes. Thus, the daytime atmosphere is filled with extra oxygen.

Uses of Oxygen Molecule

The main uses of oxygen are in melting, refining, and producing steel and other metals. It is employed in mining as well as the making and fabrication of glass and stone items.

Medical oxygen therapy can be used to address low oxygen levels. Treatment with oxygen molecules helps to raise blood oxygen levels and has the added benefit of lowering blood flow resistance in the weak lung, which reduces the stress placed on the heart and lungs.

Oxygen molecule treatment can also treat congestive heart failure, emphysema, pneumonia, some medical conditions that increase pressure on pulmonary arteries, and any illness that affects the body’s capacity to absorb and use gaseous oxygen. 


Although oxygen does not burn on its own, it is a necessary element for combustion. Along with heat and fuel, O2 molecules are also required for combustion. The heat produced by the fuel maintains the fire. The fire will keep burning until the fuel and oxygen molecules are there. Water-based extinguishers work by eliminating all heat from the fire area. Extinguishers that use dry chemicals and carbon dioxide suppress the flames by cutting off the oxygen supply.


Dioxygen is one of the frequently seen forms of oxygen. Oxygen is a tasteless, odourless, and colourless gas. Life cannot exist without the molecular form of oxygen. Although it is non-combustible, combustible elements can be burned actively with its help. Except for neon, helium, krypton, and argon, it reacts with every element and produces oxides with them. 

Frequently Asked Questions

Q) What is the molecular composition of oxygen molecules?

A) Oxygen is a non-metallic element that exists naturally as a molecule. When two oxygen atoms combine, they make up one O2 molecule. Oxygen is in a gaseous state at ambient temperature due to its low melting and boiling temperatures.

Q) What is another name for an oxygen molecule?

A) O2 molecules are also referred to as dioxygen; these are molecules made up of two oxygen atoms that share two pairs of electrons. Dioxygen is the second most common gas present in the earth’s atmosphere.

Q) What are the uses of oxygen molecules?

A) Oxygen can be used both naturally and commercially. The stratosphere’s oxygen, ozone, forms a barrier that shields living things from the sun’s ultraviolet rays. Additionally, it is the second-most prevalent gas in our environment and aids in breaking glucose into cellular energy for organisms. Researchers have also shown that liquid oxygen and hydrogen may be combined to make rocket fuel. Additionally, ozone can be used to disinfect water.

Molecule of Oxygen


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