Difference Between Oxygen and Air

Oxygen vs Air

Air or atmosphere is a main component of the Earth, other than water (hydrosphere) and soil (lithosphere). Four and a half billion years ago, when the earth was forming, the atmosphere consisted of gases like hydrogen, nitrogen, carbon dioxide, water vapor, hydrogen sulfide, ammonia and methane only. There was no oxygen in the atmosphere. The first living organisms evolved around 3.5 billion years ago and they were not depending on oxygen for their energy production. Later, photosynthetic organisms evolved and they started releasing oxygen to the atmosphere as a by-product of photosynthesis. As a result of increasing oxygen in the atmosphere, organisms adapted to utilize oxygen.


Air is a collection of various gases in different quantities, water vapor, and particulate matter. Nitrogen (78%), oxygen (21%), argon (0.9%) and carbon dioxide (0.03%) gases make up to 99.99 % of the air. Other gases like neon, helium, krypton, sulfur dioxide, hydrogen, methane and ammonia are only present in minute concentrations and therefore, known as trace gases. Air is important for the climate patterns, and to absorb harmful solar energy, sound wave propagation, etc. Depending on the composition of air, it may have a color or odor, but naturally, air is colorless and odorless. If there are more particulate matters, for example, where a factory fumes are emitted, air may have a dark color and an odor of chemicals. Air pollution is the deterioration of the quality of air by releasing substances or energy in such quantities, which prevent smooth/ balanced functioning of natural processes and produce undesirable environmental and health effects. Main air pollutants are sulfur dioxide, nitrogen oxides, carbon monoxide, hydrocarbons, particulate matter, CFC, carbon dioxide and ozone. These are emitted due to human activities, and it has resulted in various a global problems now.


Oxygen is the element with the atomic number 8, which is present in group 16 of the periodic table. Oxygen has three isotopes, 16O, 17O, 18O. Among these 16O is the most abundant isotope. Oxygen atom has eight electrons, and it can obtain two more electrons from another atom to form a -2 charged anion. Alternatively, two oxygen atoms can share four electrons to form a diatomic molecule (O2) to be stable. Molecular weight of O2 is 32 g mole-1. Three atomic form of oxygen, which is also known as ozone is another common form of oxygen. Molecular oxygen is a colorless, odorless gas. There is about 21% of oxygen in the earths’ atmosphere. It is poorly soluble in water and is slightly heavier than air. Oxygen reacts with all the elements to form oxides except inert gases. Therefore, it is a good oxidizing agent. Oxygen is essential in respiration of living organisms and also for the combustion. Oxygen is used in hospitals, welding, and in many other industries.

Difference Between Air and Oxygen

- Oxygen is only a part of air/ atmosphere.

- Oxygen concentration in air is about 21% by volume, and it is the second abundant gas after nitrogen.

- Oxygen in air is especially important for the survival of living organisms, along with some other components.