|Atomic Number:||8||Atomic Symbol:||O|
|Atomic Weight:||15.9994||Electron Configuration:||2-6|
|Melting Point:||-218.4oC||Boiling Point:||-183.0oC|
|Uses:||Combustion, life support, welding, steel making etc. |
History(Gr. oxys, sharp, acid, and genes, forming; acid former) For
many centuries, workers occasionally realized air was composed of more than one
component. The behavior of oxygen and nitrogen as components of air led to the
advancement of the phlogiston theory of combustion, which captured the minds of
chemists for a century.
Oxygen was prepared by several workers, including Bayen and Borch, but they
did not know how to collect it, did not study its properties, and did not
recognize it as an elementary substance.
Joseph Priestley of England is generally credited with its dicovery, although
Carl Wilhelm Scheele of Sweden also discovered it independently.
Its atomic weight was used as a standard of comparison for each of the other
elements until 1961 when the International Union of Pure and Applied Chemistry
adopted carbon 12 as the new basis.
SourcesOxygen is the third most abundant element found in the sun, and
it plays a part in the carbon-nitrogen cycle, the process once thought to give
the sun and stars their energy. Oxygen under excited conditions is responsible
for the bright red and yellow-green colors of the Aurora.
A gaseous element, oxygen forms 21% of the atmosphere by volume and is
obtained by liquefaction and fractional distillation. The atmosphere of Mars
contains about 0.15% oxygen. The element and its compounds make up 49.2%, by
weight, of the earth's crust. About two thirds of the human body and nine tenths
of water is oxygen.
In the laboratory it can be prepared by the electrolysis of water or by
heating potassium chlorate with manganese dioxide as a catalyst.
FormsThe gas is colorless, odorless, and tasteless. The liquid and
solid forms are a pale blue color and are strongly paramagnetic. Ozone (O3), a
highly active compound, is formed by the action of an electrical discharge or
ultraviolet light on oxygen.
Ozone's presence in the atmosphere (amounting to the equivalent of a layer 3
mm thick under ordinary pressures and temperatures) helps prevent harmful
ultraviolet rays of the sun from reaching the earth's surface. Pollutants in the
atmosphere may have a detrimental effect on this ozone layer. Ozone is toxic and
exposure should not exceed 0.2 mg/m# (8-hour time-weighted average - 40-hour
work week). Undiluted ozone has a bluish color. Liquid ozone is bluish black and
solid ozone is violet-black.
CompoundsOxygen, which is very reactive, is a component of hundreds of
thousands of organic compounds and combines with most elements.
UsesPlants and animals rely on oxygen for respiration. Hospitals
frequently prescribe oxygen for patients with respiratory ailments.
IsotopesOxyen has nine isotopes. Natural oxygen is a mixture of three
Natural occurring oxygen 18 is stable and available commercially, as is water
(H2O with 15% 18-O). Commercial oxygen consumption in the U.S. is
estimated at 20 million short tons per year and the demand is expected to
Oxygen enrichment of steel blast furnaces accounts for the greatest use of
the gas. Large quantities are also used in making synthesis gas for ammonia and
methanol, ethylene oxide, and for oxy-acetylene welding.
Air separation plants produce about 99% of the gas, while electrolysis plants
produce about 1%.
CostsThe gas costs 5 cents / ft3 in small quantities, and
about $15/ton in large quantities