Oxygen

Nitrogen - Oxygen - Fluorine   O S       Full table
General
Name, Symbol, Number	Oxygen, O, 8
Chemical series	nonmetals
Group, Period, Block	16 (VIA), 2 , p
Density, Hardness	1.429 kg/m3 (273K), NA
Appearance	colorless
Atomic Properties
Atomic weight	15.9994 amu
Atomic radius (calc.)	60 (48) pm
Covalent radius	73 pm
van der Waals radius	152 pm
Electron configuration	[He]2s2s22p4
e- 's per energy level	2, 6
Oxidation states (Oxide)	-2,-1 (neutral)
Crystal structure	cubic
Physical Properties
State of matter	gas (paramagnetic)
Melting point	50.35 K (-368.77 °F)
Boiling point	90.18 K (-297.08 °F)
Molar volume	17.36 ×1010-3 m3/mol
Heat of vaporization	3.4099 kJ/mol
Heat of fusion	0.22259 kJ/mol
Vapor pressure	__ Pa at __ K
Speed of sound	317.5 m/s at 293 K
Miscellaneous
Electronegativity	3.44 (Pauling scale)
Specific heat capacity	920 J/(kg*K)
Electrical conductivity	__ 106/m ohm
Thermal conductivity	0.02674 W/(m*K)
1st ionization potential	1313.9 kJ/mol
2nd ionization potential	3388.3 kJ/mol
3rd ionization potential	5300.5 kJ/mol
4th ionization potential	7469.2 kJ/mol
Most Stable Isotopes
iso NA half-life DM DE MeV DP 16O 99.762% O is stable with 8 neutrons 17O 0.038% O is stable with 9 neutrons 18O 0.2% O is stable with 10 neutrons
SI units & STP are used except where noted.

Oxygen is a chemical element in the periodic table that has the symbol O and atomic number 8. The element is common and ubiquitous, found not only on Earth but throughout the universe. Molecular oxygen (O₂), as on Earth, is thermodynamically unstable, but exists through the action, first, of photosynthetic anaerobes and, in later epochs, of photosynthetic terrestrial plants.

Table of contents

1 Notable Characteristics 2 Applications 3 History 4 Occurrence 5 Compounds 6 Isotopes 7 Precautions 8 See also 9 External Links

Notable Characteristics

At standard temperature and pressure, oxygen is found as a gas consisting of two oxygen atoms, chemical formula O₂. This oxygen is an important component of air, produced by plants during photosynthesis and is necessary for animals' respiration. The word oxygen derives from two words in Greek, the Greek oxus (acid) and gennan (generate).

Liquid oxygen and solid oxygen have a light blue color and both are highly paramagnetic. Liquid oxygen is usually obtained by the fractional distillation of liquid air.

Applications

Oxygen finds considerable use as an oxidizer, with only fluorine having a higher electronegativity. Liquid oxygen finds use as an oxidizer in rocket propulsion. Oxygen is essential to respiration, so oxygen supplementation has found use in medicine. People who climb mountains or fly in airplanes sometimes have supplemental oxygen supplies (as air). Oxygen is used in welding, and in the making of steel and methanol.

Oxygen, as a mild euphoric, has a history of recreational use that extends into modern times. Oxygen bars can be seen at parties to this day. In the 19th century, oxygen was often mixed with nitrous oxide to promote a kind of analgesic effect.

History

Oxygen was discovered by the Swedish pharmacist Karl Wilhelm Scheele in 1771, but this discovery was not immediately recognized, and the independent discovery by Joseph Priestley was more widely known. It was named by Antoine Laurent Lavoisier in 1774.

Occurrence

Oxygen is the most abundant element in the Earth's crust, estimated to comprise 46.7% of the crust. Oxygen comprises about 87% of the oceans (as H₂O, water) and 20% of the atmosphere of Earth (as O₂, molecular oxygen, or O₃, ozone). Oxygen compounds, particularly metal oxides, silicates (SiO₄^4-) and carbonates (CO₃^2-), are commonly found in rocks and soil. Frozen water is a common solid on the outer planets and comets. The ice caps of Mars are made of frozen carbon dioxide. Oxygen compounds are found throughout the universe and the spectrum of oxygen is often seen in stars. In fact stars wouldn't produce light without oxygen.

Compounds

Due to its electronegativity, oxygen forms chemical bonds with almost all other elements (which is the origin of the original definition of oxidation). The only elements to escape the possibility of oxidation are a few of the noble gases. The most famous of these oxides is of course hydrogen oxide, or water (H₂O). Other well known examples include compounds of carbon and oxygen, such as carbon dioxide (CO₂), alcohols (R-OH), aldehydes, (R-CHO), and carboxylic acids (R-COOH). Oxygenated radicalss such as chlorates (ClO₃^-), perchlorates (ClO₄^-), chromates (CrO₄^2-), dichromates (Cr₂O₇^2-), permanganates (MnO₄^-), and nitrates (NO₃^-)are strong oxidizing agents in and of themselves. Many metals such as Iron bond with oxygen atoms, Ferric Oxide (Fe₂O₃). Ozone (O₃) is formed by electrostatic discharge in the presence of molecular oxygen. A double oxygen molecule (O₂)₂ is known, found as a minor component of liquid oxygen. Epoxides are ethers in which the oxygen atom is part of a ring of three atoms.

Isotopes

Oxygen has three stable isotopes and ten known radioactive isotopes. The radioisotopes all have half lives of less than three minutes.

Precautions

Prolonged exposure to pure oxygen at higher pressures can be toxic, having both pulmonary and neurological effects. Pulmonary effects include edema, loss of lung capacity and damage to lung tissues. Neurological effects can include loss of vision, convulsions and coma.

Certain derivatives of oxygen, such as ozone (O₃), hydrogen peroxide, hydroxyl radicals and superoxide, are also highly toxic. The body has developed mechanisms to protect against these toxic species. For instance, the naturally-occurring glutathione can act as an antioxidant, as can bilirubin which is normally a breakdown product of hemoglobin. Highly concentrated sources of oxygen promote rapid combustion and therefore are fire and explosion hazards in the presence of fuels. This is true as well of compounds of oxygen such as chlorates, perchlorates, dichromates, etc. Compounds with a high oxidative potential can often cause chemical burns.

The fire that killed the Apollo 1 crew on a test lauchpad spread so rapidly because the pure oxygen atmosphere was at normal atmospheric pressure instead of the one third pressure that would be used during an actual launch. (see partial pressure)

See also

• Winkler test for dissolved oxygen for instructions on how to determine the amount of oxygen dissolved in fresh water.
• Combustion.
• Oxidation.

• Los Alamos National Laboratory - Oxygen
• WebElements.com - Oxygen
• EnvironmentalChemistry.com - Oxygen
• It's Elemental - Oxygen
• Oxygen Therapy - The First 150 Years
• Oxygen Toxicity

Oxygen is also the name of a Cable TV channel in the US. Its programming targets women audience.