Oxygen
Oxygen [O]
CAS-ID: 7782-44-7
An: 8 N: 8
Am: 15.9994 (3) g/mol
Group No: 16
Group Name: Chalcogen
Block: p-block Period: 2
State: gas at 298 K
Colour: colourless as a gas, liquid is pale blue Classification: Non-metallic
Boiling Point: 90.2K (-182.9°C)
Melting Point: 54.8K (-218.3°C)
Critical temperature: 154.6K (-118.5°C)
Density: 1.429g/l

Discovery Information
Who: Joseph Priestley, Karl Wilhelm Scheele
When: 1774
Where: England/Sweden

Name Origin
Greek: oxus (acid) and gennan (generate).

Sources
Obtained primarily from by liquification and then fractional distillation of the air. World wide production is around 100 million tons.

Abundance
Universe: 10000 ppm (by weight)
Sun: 9000 ppm (by weight)
Carbonaceous meteorite: 4.1 x 105 ppm
Atmosphere: 2.095 x 105 ppm
Earth's Crust: 4.74 x 105 ppm
Human:
6.1 x 108 ppb by weight
2.4 x 108 ppb by atoms

Uses
Used in steel making, production of methanol (CH3OH), welding, water purification, cement and rocket propulsion. It is also required for supporting life and combustion. Oxygen is a major component of air, produced by plants during photosynthesis, and is necessary for aerobic respiration in animals.

History
Oxygen was first described by Michal Sedziwoj, a Polish alchemist and philosopher in the late 16th century. Sedziwoj thought of the gas given off by warm niter (saltpeter) as "the elixir of life".

Oxygen was more quantitatively discovered by the Swedish pharmacist Karl Wilhelm Scheele some time before 1773, but the discovery was not published until after the independent discovery by Joseph Priestley on August 1, 1774, who called the gas dephlogisticated air. Priestley published discoveries in 1775 and Scheele in 1777; consequently Priestley is usually given the credit. Both Scheele and Priestley produced oxygen by heating mercuric oxide.

Scheele called the gas 'fire air' because it was the only known supporter of combustion. It was later called 'vital air' because it was and is vital for the existence of animal life.

The gas was named by Antoine Laurent Lavoisier, after Priestley's publication in 1775, from Greek roots meaning "acid-former". As noted, the name reflects the then-common incorrect belief that all acids contain oxygen. This is also the origin of the Japanese name of oxygen "sanso" (san=acid, so=element).

Oxygen was first time condensed in 1883 by professors of Jagiellonian University - Zygmunt Wroblewski (Polish chemist) Karol Olszewski (Polish physicist and chemist).

Notes
Liquid and solid O2 are both a light blue colour. Ozone (O3) is a deeper blue colour. Oxygen is the second most common element on Earth, composing around 46% of the mass of Earth's crust (the most common element) and 28% of the mass of Earth as a whole, and is the third most common element in the universe. Forms almost 21% of atmosphere.

Hazards
Certain derivatives of oxygen, such as ozone (O3), singlet oxygen, hydrogen peroxide (H2O2), hydroxyl radicals and superoxide (O2-), are highly toxic. Highly concentrated sources of oxygen promote rapid combustion and therefore are fire and explosion hazards in the presence of fuels.


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