Oxygen is the most essential gas that makes life possible on Earth. Physically, the gas is colourless, odourless and tasteless. At standard temperature and pressure, Oxygen is usually found as dioxygen O2. Most oxygen on the surface of the Earth are found as O2, making up about 20.8% of the atmosphere. Most of the oxygen comes from the plants by the process of photosynthesis. In the stratosphere region, the second form of oxygen can be found as a layer of ozone O3 about 10 ppm, absorbing 99% of the Sun's ultraviolet radiation. O2 can be condensed to a blue liquid form as liquid oxygen. Oxygen, due to its electronegativity, is highly reactive and it readily oxidizes organic materials. Trioxygen (ozone) can also be condensed to a highly unstable liquid form of liquid ozone as well.

Frequently Asked Questionsedit

Why oxygen is highly reactive?edit

The reactive property of Oxygen is because of the high electronegativity of the oxygen atom. The valence shell of the atom has six electrons and hence it has the tendency to attract two more electrons from other atoms and bonds with them to form stable oxides. This makes oxygen a highly reactive element.

Is pure oxygen dangerous for humans?edit

Pure oxygen or too much oxygen inside the human system is dangerous as oxygen can oxidize more molecules and increase the number of free radicals in the system. Free radicals are the atoms with unpaired electrons in its valence shell. Once oxygen reacts with atoms in the human body to form free radicals [1], the balance between the radicals and antioxidants are disturbed and leads to a chain reaction, causing elevated levels of oxidative stress. The condition, if not controlled, could lead to the damage of vital molecules like DNA, and cause irreversible fatal damages.


  1. Vento, M., Asensi, M., Sastre, J., Garcı́a-Sala, F., Pallardó, F., & Viña, J. (2017). Resuscitation With Room Air Instead of 100% Oxygen Prevents Oxidative Stress in Moderately Asphyxiated Term Neonates. Pediatrics.aappublications.org. Retrieved 29 March 2017, from http://pediatrics.aappublications.org/content/107/4/642