| Oxygen - O
CAS: 7782-44-7 Description: Colorless, odorless, tasteless gas Classification: Non-metal Date of Discovery: 1774 Discoverer: Joseph Priestly Name Origin: Greek oxys, "sharp", "acid, and genes, "forming"; "acid former" |
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Atomic Number: 8
Number of Neutrons: 8 Atomic Mass: 15.9994(3) amu Melting Point: -218.7916 °C Boiling Point: -182.95 °C Density (293 K): 1.429 g/cm3 Atomic volume: 14.0 cm3/mol Electrical resistivity: Thermal conductivity: 0.0002674 W/cmK Enthalpy of atomization: 249.37 kJ/mol Enthalpy of vaporization: 3.4099 kJ/mol Enthalpy of fusion: 0.22259 kJ/mol Specific heat capacity: 0.92 J/gK |
Energy levels: 2-6
Electron configuration: [He]2s22p4 Crystal Structure: Cubic Atomic radius: 0.65 Å Covalent radius: 0.73 Å Oxidation States: -2 Electronegativity, Pauling: 3.44 Electron affinity: 1.4611103 eV First ionization energy: 13.618 eV 2nd ionization energy: 35.117 eV 3rd ionization energy: 54.934 eV Polarizability: 0.802 10-24cm3 |
| Isotope | Natural Abundance | Atomic Mass | Half-life | Decay Mode | Spin |
| 12O | 12.03442 |  1 x 10-21 s |
2p | ||
| 13O | 13.02481 | 8.9 ms |  +, p |
(3/2-) | |
| 14O | 14.0085953 | 70.60 s | + |
0+ | |
| 15O | 15.003065 | 122.2 s | + |
1/2- | |
| 16O | 99.762(15) | 15.99491462 | Stable | 0+ | |
| 17O | 0.038(3) | 16.9991315 | Stable | 5/2+ | |
| 18O | 0.200(12) | 17.99160 | Stable | 0+ | |
| 19O | 19.003577 | 26.9 sec | - |
5/2+ | |
| 20O | 20.004076 | 13.5 s | - |
0+ | |
| 21O | 21.00866 | 3.4 s | - |
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| 22O | 22.00997 | 2.2 | - |
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| 23O | 23.0157 | 0.08 s | |||
| 24O | 24.0204 | 0.06 s | - |
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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. Priestley is generally credited with its
discovery, although Scheele also discovered it independently. Oxygen is the third most abundant element found in the sun, and it plays a part in the carbon-nitrogen cycle, one process 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. Oxygen, as a gaseous element, forms 21% of the atmosphere by volume from which it can be 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. The 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 at ordinary pressures and temperatures) is of vital importance in preventing harmful ultraviolet rays of the sun from reaching the earth's surface. There has been recent concern that pollutants in the atmosphere may have a detrimental effect on this ozone layer. Ozone is toxic and exposure should not exceed 0.2 mg/cu 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. Oxygen is very reactive and capable of combining with most elements. It is a component of hundreds of thousands of organic compounds. It is essential for
respiration of all plants and animals and for practically all combustion. In hospitals it is frequently used to aid respiration of patients. 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. Oxygen has thirteen recognized isotopes. Natural oxygen is a mixture of three isotopes. 18O occurs naturally, is stable, and is available commercially. Water (H20 with 1.5% 18O) is also available. Commercial oxygen consumption in the U.S. is estimated to be 20 million short tons per year and the demand is expected to increase substantially in the next few years. 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 oxyacetylene welding. Air separation plants produce about 99% of the gas, electrolysis plants about 1%.
LINKS: EPA: Ozone Depletion Hyperbaric Oxygen Therapy Information Center International Ozone Association NOVA Online - Warnings from the Ice Oxygen Isotope Study of the Princess Elizabeth Trough, Antarctica The Oxygen Society Space Shuttle: Main Prpoulsion System Thermal conductivity of solid oxygen Return
Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998. |
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