Difference between revisions of "Oxygen"

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(Created page with "{{stub}} An '''oxide''' is a type of chemical which contains oxygen bonded to another element. The terminology is usually used to refer to inorganic compounds, where the oxyge...")
 
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An '''oxide''' is a type of chemical which contains oxygen bonded to another element. The terminology is usually used to refer to inorganic compounds, where the oxygen is not part of a polyatomic anion.
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'''Oxygen''' is the 8th element on the periodic table and is the second strongest [[oxidizer]], second to fluorine. It has the atomic weight of ~16 (15.9949), but as a gas it is diatomic with a molar mass of ~32.
  
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==Types==
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==Properties==
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All metals form oxides. Lower oxides of [[transition metals]] tend to have color to them, while higher transition metal oxides are black due to a nonstoichiometric composition, or white due to the lack of d-shell electrons. Other metal oxides are often white due to the complete lack of d-shell electrons. Most metal oxides are basic, and will combine with water to form [[hydroxides]]. Few of these, however, are soluble in water, save for the oxides of [[alkali metals]] and thallium(I). Some metal oxides are amphoteric, meaning that they can be both acidic and basic. [[Aluminum oxide]] is the most common example. Some higher oxides of metals are acidic and will form oxoacids or oxoacid anions. Some common examples are [[chromium(VI) oxide]], which forms [[chromic acid]] when dissolved, and [[chromate]]s with many other metal ions, and [[manganese heptoxide]], which forms [[permanganate]]s. More commonly, however, they form with heavier transition metals, such as [[tantalum]] and [[tungsten]].
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===Chemical===
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Oxygen has 6 valence electrons and typically exists with two lone pairs of electrons.
  
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Some nonmetals form oxides, which tend to be a [[gas]] at normal temperatures, though some are solid or liquid. Most nonmetal oxides are [[Acid|acidic]], and many will combine with water to form an acid. Most nonmetal oxides are soluble in water. A few, however, are insoluble, notably [[carbon dioxide]] and [[sulfur dioxide]]. These can both be captured by [[Base|basic]] solutions and stored as [[carbonate]]s and [[sulfite]]s, respectively.
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It is highly electronegative, with a 3.44 on the Pauling scale. It reacts directly with almost every element, a major exception being most of the noble metals and gases (except for [[xenon]]).
  
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When considered 'ions', an oxide has -2 charge per oxygen, except in [[Peroxide|peroxides]], where both oxygen atoms have a charge of -1 each. Superoxide ions contain two oxygen atoms with an overall charge of -1, forming a [[radical]]. One example of a metal oxide is [[copper(II) oxide]], with the formula CuO. All metals can form oxides, but some form oxides more easily than others. For example: [[Iron(III) oxide|rust]] forms on iron easily, but gold is not normally oxidized by the oxygen in the air.
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It reacts with many metals to form oxides. These reactions can be slow and gradual (as is the rusting of [[iron]]) or extremely fast, as in the combustion of [[cesium]].
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===Physical===
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Although in gas form it is indistinguishable from other common gases, in liquid form it is pale blue (and highly reactive). Oxygen is paramagnetic.
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==Availability==
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Gaseous oxygen makes up 21% of the atmosphere. For higher concentrations, compressed oxygen can be procured from the companies that sell welding products as well as scuba diving stores. Cryogenic liquid oxygen is harder to get because unlike liquid [[nitrogen]] it is a fire and explosive hazard, when it (accidentally) enters in contact with organic materials.
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==Preparation==
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Oxygen is extracted from air by fractional distillation on an industrial scale.
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In the lab, it can be isolated by:
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* electrolysis of [[water]] with containing ions
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* heating [[potassium chlorate]] with [[manganese dioxide]],
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* decomposing [[hydrogen peroxide]] with manganese dioxide
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* Decomposition of hypochlorite solution (laundry bleach) using a small amount of cobalt chloride as a catalyst
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* heating potassium permanganate.
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A way to make liquid oxygen involves liquifying normal air with liquid nitrogen and collecting the oxygen-rich layer on top.
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==Safety==
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Atmospheric oxygen is not a hazard to health, however at high concentration it becomes dangerous to the lungs and can cause blindness. At concentrations over 50%, it will greatly amplify any exothermic reaction. Liquid oxygen is a fire and explosive hazard when in contact with organic materials and a fire source. It can also cause frostbites if it touches the skin.
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==References==
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<references/>
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==Relevant Sciencemadness threads==
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*[http://www.sciencemadness.org/talk/viewthread.php?tid=23211 LOX (Liquid Oxygen)]

Revision as of 07:11, 14 June 2015

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Oxygen is the 8th element on the periodic table and is the second strongest oxidizer, second to fluorine. It has the atomic weight of ~16 (15.9949), but as a gas it is diatomic with a molar mass of ~32.

Properties

Chemical

Oxygen has 6 valence electrons and typically exists with two lone pairs of electrons.

It is highly electronegative, with a 3.44 on the Pauling scale. It reacts directly with almost every element, a major exception being most of the noble metals and gases (except for xenon).

It reacts with many metals to form oxides. These reactions can be slow and gradual (as is the rusting of iron) or extremely fast, as in the combustion of cesium.

Physical

Although in gas form it is indistinguishable from other common gases, in liquid form it is pale blue (and highly reactive). Oxygen is paramagnetic.

Availability

Gaseous oxygen makes up 21% of the atmosphere. For higher concentrations, compressed oxygen can be procured from the companies that sell welding products as well as scuba diving stores. Cryogenic liquid oxygen is harder to get because unlike liquid nitrogen it is a fire and explosive hazard, when it (accidentally) enters in contact with organic materials.

Preparation

Oxygen is extracted from air by fractional distillation on an industrial scale.

In the lab, it can be isolated by:

  • electrolysis of water with containing ions
  • heating potassium chlorate with manganese dioxide,
  • decomposing hydrogen peroxide with manganese dioxide
  • Decomposition of hypochlorite solution (laundry bleach) using a small amount of cobalt chloride as a catalyst
  • heating potassium permanganate.

A way to make liquid oxygen involves liquifying normal air with liquid nitrogen and collecting the oxygen-rich layer on top.

Safety

Atmospheric oxygen is not a hazard to health, however at high concentration it becomes dangerous to the lungs and can cause blindness. At concentrations over 50%, it will greatly amplify any exothermic reaction. Liquid oxygen is a fire and explosive hazard when in contact with organic materials and a fire source. It can also cause frostbites if it touches the skin.

References

Relevant Sciencemadness threads

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