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Topic: Allotrope


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In the News (Mon 18 Dec 17)

  
  Allotropy - Wikipedia, the free encyclopedia
Allotropy specifically refers to the chemical bond structure between atoms of the same kind and should not be confused with the existence of multiple physical states, such as with water, which can exist as a gas (steam), a liquid (water), or a solid (ice).
These phases of water are not allotropes, since they are caused by changes in the physical bonding between water molecules, rather than changes in the chemical bonding of the water molecules themselves.
The structure of fullerenes (a carbon allotrope found in soot) resembles that of graphite, except that instead of hexagons of carbon atoms, smaller regular polygons are formed, such as a mix of hexagons and pentagons, such that the sheet can fold back onto itself into closed spheroids, as with the seams of a soccer ball.
en.wikipedia.org /wiki/Allotrope   (452 words)

  
 Science : Allotropes   (Site not responding. Last check: 2007-11-07)
The allotropes are usually due to the crystal shape, or lack of crystal shape, or the attachments of more than one atom of an element.
Allotrope comes from the word allotropy that means the ability of certain element to being in more than one physical state.
This term is usually associated with enantropy (the existence of different allotropes of and elements at different temperatures) and monotropy (the existence of a single allotrope of an element independent of temperature).
www.seed.slb.com /qa2/FAQView.cfm?ID=868   (141 words)

  
 Diamond - Wikipedia, the free encyclopedia
The mineral diamond is a crystalline form, or allotrope, of carbon (other allotropes of carbon include graphite, fullerene and ceraphite).
The tetrahedral arrangement of atoms in a diamond crystal is the source of many of diamond's properties; graphite, another allotrope of carbon, has a rhombohedral crystal structure and as a result shows dramatically different physical characteristics — contrary to diamond, graphite is a very soft, dark grey opaque mineral.
However, aggregated diamond nanorods, an allotrope of carbon first synthesised in 2005, are now believed to be even harder than diamond.
en.wikipedia.org /wiki/Diamond   (8228 words)

  
 MSN Encarta - Search Results - Allotrope
Allotrope, two or more distinct physical forms of a chemical element in the same physical state.
Three structural forms of oxygen are known: ordinary oxygen, containing two atoms per molecule, formula O
Allotropes are different physical forms of the same element, such as a hard, highly structured crystal and a soft,...
encarta.msn.com /Allotrope.html   (89 words)

  
 Chemical Forums: Ask a Chemistry Question -   (Site not responding. Last check: 2007-11-07)
The three main allotropes of phosphorus are white phosphorus, red phosphorus, and fl phosphorus.
Of all the allotropes of phosphorus, the red version is the most “stable.” That is, both the white and fl allotropes will tend to convert themselves into the red allotrope over time.
This may be due to fact that the crystal structure of red phosphorus is kind of halfway in between that of the white and fl allotropes.
www.chemicalforums.com /index.php?op=articles;id=16   (2283 words)

  
 INTRODUCING OZONE   (Site not responding. Last check: 2007-11-07)
Allotropes are molecules composed of a single element.
In the case of an allotrope all the atoms are from the same element.
Even though these allotropes both contain the element oxygen, they have different molecular structures.
coolspace.gsfc.nasa.gov /hawaii/lessons/introducing_ozone1.htm   (476 words)

  
 Phosphorus articles and news from Start Learning Now   (Site not responding. Last check: 2007-11-07)
A fl phosphorus allotrope exists which has a structure similar to graphite – the atoms are arranged in hexagonal sheet layers and will electrical conductionconduct electricity.
This is a particularly poisonous element with 50 milligrammg being the average fatal dose (white phosphorus is generally considered to be the lethal form of phosphorus while phosphate and orthophosphate are essential nutrients).
The allotrope white phosphorus should be kept under water at all times and therefore presents a significant fire hazard due to its extreme reactivity to atmospheric oxygen, and it should only be manipulated with forceps since contact with skin can cause severe burns.
www.startlearningnow.com /phosphorus.htm   (1420 words)

  
 Lateral Science - Explosive Antimony   (Site not responding. Last check: 2007-11-07)
The explosive antimony (alpha-antimony allotrope with between 4 and 20% antimony trichloride) is deposited on the cathode and, in appearance, looks like polished graphite.
If the deposit is scratched, the meta-stable allotrope is violently converted into the stable allotrope (common, or beta antimony) with the evolution of heat.
Here are a couple of extracts about antimony in which the explosive allotrope is mentioned (large graphics files).
www.lateralscience.co.uk /Fluorine/exant.html   (198 words)

  
 Sandia National Laboratories - Albuquerque, NM:Computer-Aided Molecular Design - Fullerenes
Fullerenes are the third structural form (or allotrope) of carbon.
Discovered in late 1990, this new allotrope is being intensely investigated in universities, industry, and at Sandia-California.
Fullerenes are geometrically hollow spheroidal arrays of carbon hexagonal and pentagonal rings formed into a geodesic dome-like structure and have possible use in advanced materials in electronic, optical, structural, and high energy (rocket fuel) applications.
www.bmpcoe.org /bestpractices/internal/sandi/sandi_26.html   (303 words)

  
 Chemistry and Industry: Buckminsterfullerene: the third allotrope of carbon. (Postgraduate Essay Competition)@ HighBeam ...   (Site not responding. Last check: 2007-11-07)
Chemistry and Industry: Buckminsterfullerene: the third allotrope of carbon.
In 1985 Harry Kroto and his colleagues at Rice University, Texas proposed to the world that they thought they had discovered a new allotrope of carbon.
This in itself was an amazing announcement as previously scientists had believed there were only two forms of carbon - graphite and diamond - but even more intriguing were the proposed shape and possible properties of this new form of carbon.
www.highbeam.com /library/doc0.asp?DOCID=1G1:10804395&refid=ip_encyclopedia_hf   (175 words)

  
 Ozone - the free encyclopedia   (Site not responding. Last check: 2007-11-07)
) is an allotrope of oxygen, the molecule consisting of three oxygen atoms instead of themore stable diatomic O
At standard temperature andpressure ozone is a blue gas.
Ozone has been studied extensively, and found to be carcinogenic to some animals (and not others), and a mutagen to somebacteria.
www.free-web-encyclopedia.com /?t=O3   (800 words)

  
 Chem453Web
A New Allotrope of Carbon?" In 1995, Lagow et al.
Critique these papers by succinctly summarizing (a) the synthesis and the experimental basis for the proposed structure (b) the reasons to be skeptical about the assignment and characterization, and (c) whether or not such a material (if it exists) should be considered a true allotrope.
Lagow (from the University of Texas at Austin) is scheduled to give a research seminar on this topic on Tuesday February 24 at noon (probably in Seaver Science Center Auditorium).
www-scf.usc.edu /~chem453/page2.html   (480 words)

  
 Allotropy : Allotrope   (Site not responding. Last check: 2007-11-07)
allos, other, and tropos, manner), a name applied by Jons Jacob Berzelius to the property possessed by certain substances of existing in different modifications; the various forms are known as allotropes.
Some classic examples of elements that have allotropes, are phosphorus (in "red" and "white" forms) and carbon (in the form of graphite, diamond, or fullerenes).
The structure of fullerenes (a carbon allotrope found in soot) resembles that of graphite, except that instead of hexagons of carbon atoms, smaller polygons are formed, such as a mix of hexagons and pentagons, such that the sheet can fold back onto itself into closed spheroids, as with the seams of a soccer ball.
www.termsdefined.net /al/allotrope.html   (622 words)

  
 #1 Site For Learning Chemistry
Two allotropic forms commonly seen are: red phosphorus and yellow (or white) phosphorus.
Phosphorus is indispensable to all living organisms; it is needed in bones, it is used for converting food into useful form of energy.
White P is unstable and converts to its more stable allotrope, the red P. When white P can be heated to 250°C in an inert atmosphere (so that it doesn’t catch fire) of nitrogen or carbon dioxide, it converts to red P. White P smells like garlic.
home.att.net /~cat6a/metals-XVIII.htm   (1065 words)

  
 PFA Glossary
An allotrope is a specific crystal structure of the metal.
The low-temperature allotrope of titanium with a hexagonal, close-packed crystal structure.
Producing a beta phase by heating certain titanium alloys in the temperature range of which this phase forms followed by cooling at an appropriate rate to prevent its decomposition.
www.asm-intl.org /meionline/21442K/common/html/Ti_glossary.htm   (11275 words)

  
 The Actinide Research Quarterly: 4th Quarter 2000
It is extremely important to understand the character of the electrons near the Fermi energy (outermost) of the material because these electrons in particular are involved in bonding or conduction and collectively form the valence band of the solid.
Analysis of the plasmon response of the material over the range of primary electron energies that were used shows substantial changes as the depth of material sampled by the spectroscopy changes from approximately 8 to 18 Å.
A compilation of the 700 eV EELS spectra for each thermal allotrope exhibits subtle shifts in the energy of the plasmon resonance peaks as a result of changes in the free electron volume density with the allotrope.
www.lanl.gov /orgs/nmt/nmtdo/AQarchive/00winter/recent.html   (1544 words)

  
 Re: Why can't safety matches be lit on sand paper?
(An allotrope is a certain crystaline arrangement of atoms in an element.
Most elements can have several possible crystaline arrangements of their atoms.) One allotrope of phosphorus is white, the other is red.
Red phosphorus,the other allotrope, is also quite reactive, but nowhere near as reactive as white phosphorus.
www.madsci.org /posts/archives/aug97/867070080.Ch.r.html   (322 words)

  
 Halfbakery: Metallic Hydrogen
Oxygen and Ozone are allotropes of that element.
Sulfur is normally found in a powdered-crystalline form, but can also exist in an allotrope that is actually somewhat rubbery in properties ("rubber sulfur" it is indeed called).
Theory indicated that very great pressure could force hydrogen to become a metallic allotrope, and the theory was somewhat verified in the laboratory about a decade ago.
www.halfbakery.com /idea/Metallic_20Hydrogen   (2152 words)

  
 CHEMTUTOR MATERIALS   (Site not responding. Last check: 2007-11-07)
Into a test tube put an amount of flowers of sulfur that is a depth of about twice the diameter of the test tube.
Carbon also has allotropes, but it is not so easy to change the carbon from one allotrope to the other.
The three allotropes of carbon are carbon fl or lampfl, diamond, and graphite.
www.chemtutor.com /ms.htm   (4168 words)

  
 tin disease and tin pest
The element oxygen, which may be found in two allotropic forms, diatomic oxygen and triatomic oxygen, provides one example.
Tin also has two allotropes: the familiar white metal, called beta-tin, and a crumbly, gray non-metallic powder known as alpha-tin.
The gradual disintegration of shiny tin metal into a crumbly, gray powder was observed hundreds of years ago on tin organ pipes housed in unheated northern European cathedrals.
dwb.unl.edu /Teacher/NSF/C10/C10Links/chemistry.about.com/library/weekly/aa040300a.htm   (693 words)

  
 Glossary
These different bonding arrangements allow for different forms of matter to be made from a single type of atom.
Different forms of matter made in this way are called allotropes.
For example, ozone (O3) and molecular oxygen (O2) are allotropes.
www.chem.wisc.edu /areas/cur_dev/CurrRef/Glossary/Glossary.html.old   (1934 words)

  
 allotrope - OneLook Dictionary Search
Tip: Click on the first link on a line below to go directly to a page where "allotrope" is defined.
allotrope : The American Heritage® Dictionary of the English Language [home, info]
Example: "Graphite and diamond are allotropes of carbon"
www.onelook.com /?w=allotrope   (167 words)

  
 Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations
A fourth allotrope of carbon, an acetylenic carbon allotrope, is described.
The acetylenic carbon allotropes of the present invention are more soluble than the other known carbon allotropes in many common organic solvents and possesses other desirable characteristics, e.g.
Many uses for this fourth allotrope are described herein.
www.osti.gov /energycitations/product.biblio.jsp?osti_id=20013980   (148 words)

  
 H2G2   (Site not responding. Last check: 2007-11-07)
- is an allotrope of carbon [An allotrope can be described as a particular molecular form of an element.
Diamond and graphite are allotropes of carbon, although it is more graphitic in nature, so strictly it is not a new allotrope, but rather a variation on graphite.
They proved that it looked like a soccer ball by showing how symmetrical it was, just as Kroto, Smalley, et al had suggested.
www.bbc.co.uk /dna/h2g2/pda/A733583   (175 words)

  
 Blue Background Template   (Site not responding. Last check: 2007-11-07)
i) The white allotrope inflames in air and has four atoms of the element in a molecule: _________
m) The only allotrope of this element is diatomic, found in the air and is very unreactive: _________
n) The element exists as two allotropes in the atmosphere, one is a diradical, the other has three atoms in its molecule and is very reactive: _________
web.utk.edu /~adcock00/p&hch21.htm   (338 words)

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