Editing Oxygen

== Explanation ==
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 '''O<sub>2</sub>'''. Most oxygen on the surface of the Earth are found as O<sub>2</sub>, 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]] '''O<sub>3</sub>''' about 10 ppm, absorbing 99% of the [[Sun]]'s [[ultraviolet]] radiation. O<sub>2</sub> can be condensed to a blue liquid form as liquid oxygen. Oxygen, due to its [[electronegativity]], is highly reactive and it readily [[oxidation|oxidizes]] organic materials. Trioxygen (ozone) can also be condensed to a highly unstable liquid form of liquid ozone as well.

== Frequently Asked Questions == 
=== Why oxygen is highly reactive? ===
The reactive property of Oxygen is because of the high electronegativity of the oxygen atom. The [[valence shell]] of the atom has six [[electron]]s and hence it has the tendency to attract two more electrons from other atoms and [[chemical bond|bonds]] with them to form stable oxides. This makes oxygen a highly reactive element.

=== Is pure oxygen dangerous for humans? ===
Pure oxygen or too much oxygen inside the human system is dangerous as oxygen can oxidize more molecules and increase the number of [[free radical]]s 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 <ref>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</ref>, the balance between the radicals and [[antioxidant]]s 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.

== References ==
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