Molecule
hideA molecule is defined as a sufficiently stable, electrically neutral group of at least two atoms in a definite arrangement held together by very strong (covalent) chemical bonds. Molecules are distinguished from polyatomic ions in this strict sense. In organic chemistry and biochemistry, the term molecule is used less strictly and also is applied to charged organic molecules and biomolecules.
In the kinetic theory of gases the term molecule is often used for any gaseous particle regardless of its composition. According to this definition noble gas atoms are considered molecules despite the fact that they are composed of a single non-bonded atom.
A molecule may consist of atoms of a single chemical element, as with oxygen (O2), or of different elements, as with water (H2O). Atoms and complexes connected by non-covalent bonds such as hydrogen bonds or ionic bonds are generally not considered single molecules.
No typical molecule can be defined for ionic crystals (salts) and covalent crystals (network solids), although these are often composed of repeating unit cells that extend either in a plane (such as in graphene) or three-dimensionally (such as in diamond or sodium chloride). The theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding. In glasses (solids that exist in a vitreous disordered state), atoms may also be held together by chemical bonds without any definable molecule, but also without any of the regularity of repeating units that characterises crystals.
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News tagged with molecules
New Synthetic Molecules Trigger Immune Response to HIV and Prostate Cancer
Nov 05, 2009 |
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(PhysOrg.com) -- Researchers at Yale University have developed synthetic molecules capable of enhancing the body’s immune response to HIV and HIV-infected cells, as well as to prostate cancer cells. Their ...
Toward home-brewed electricity with 'personalized solar energy'
Nov 04, 2009 |
3.4 / 5 (9) |
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New scientific discoveries are moving society toward the era of "personalized solar energy," in which the focus of electricity production shifts from huge central generating stations to individuals in their ...
Two-In-One Punch Knocks Out Drug Resistant Cancer Cells
Nanotechnology / Bio & Medicine
Nov 04, 2009 |
5 / 5 (4) |
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(PhysOrg.com) -- Cancer cells, like bacteria, can develop resistance to drug therapy, leading to relapse of disease. One approach showing promise in overcoming multidrug resistance in tumors is to combine two different anticancer ...
A Mars Rover Named 'Curiosity'
Space & Earth / Space Exploration
Oct 30, 2009 |
4.9 / 5 (18) |
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(PhysOrg.com) -- If you found your grandmother's diary, tattered and dust covered, up in the attic, would you read it? Of course you would. Granny was a pistol! Brush off the dust, open up the little book, ...
Alternatively spliced tissue factor identified as promising new biomarker for aggressive cancers
Oct 26, 2009 |
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A recently discovered form of the protein that triggers blood clotting may play a key role in the molecular mechanisms leading to the growth of certain metastatic cancers, according to new research reported by an international ...
Seeing Previously Invisible Molecules for the First Time
Chemistry / Analytical Chemistry
Oct 23, 2009 |
5 / 5 (7) |
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(PhysOrg.com) -- A team of Harvard chemists led by X. Sunney Xie has developed a new microscopic technique for seeing, in color, molecules with undetectable fluorescence. The room-temperature technique allows ...
Scientists first to see RNA network in live bacterial cells
Oct 22, 2009 |
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Scientists who study RNA have faced a formidable roadblock: trying to examine RNA's movements in a living cell when they can't see the RNA. Now, a new technology has given scientists the first look ever at RNA in a live ...
Synthetic Cells Shed Biological Insights While Delivering Battery Power
Oct 20, 2009 |
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(PhysOrg.com) -- Trying to understand the complex workings of a biological cell by teasing out the function of every molecule within it is a daunting task. But by making synthetic cells that include just a ...
Scientists identify specific markers that trigger aggressiveness of liver cancer
Oct 20, 2009 |
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Hepatocellular carcinoma (HCC) or primary liver cancer forms in the epithelial tissue of the liver and is most commonly caused by the hepatitis B virus (HBV) or hepatitis C virus (HCV). In the U.S., the National Cancer Institute ...
Silence of the genes
Oct 13, 2009 |
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The molecular architecture of a protein complex that helps determine the fate of human cells has been imaged for the first time by researchers with the U.S. Department of Energy's Lawrence Berkeley National ...
Dysfunctional protein dynamics behind neurological disease?
Medicine & Health / Neuroscience
Oct 13, 2009 |
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Researchers at Lund University, Sweden, have taken a snapshot of proteins changing shape, sticking together and creating structures that are believed to trigger deadly processes in the nervous system. The discovery opens ...
Magnetic nanotags spot cancer in mice earlier than methods now in clinical use
Nanotechnology / Bio & Medicine
Oct 13, 2009 |
5 / 5 (8) |
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Searching for biomarkers that can warn of diseases such as cancer while they are still in their earliest stage is likely to become far easier thanks to an innovative biosensor chip developed by Stanford University ...
Researchers create molecular diode
Oct 13, 2009 |
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Recently, at Arizona State University's Biodesign Institute, N.J. Tao and collaborators have found a way to make a key electrical component on a phenomenally tiny scale. Their single-molecule diode is described ...
Hubble observes LCROSS impact: Preliminary analysis shows no clear evidence for hydroxyl
Space & Earth / Space Exploration
Oct 12, 2009 |
4.7 / 5 (6) |
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(PhysOrg.com) -- NASA's Hubble Space Telescope has made a series of observations immediately preceding and following the Lunar Crater Observation and Sensing Satellite (LCROSS) Centaur rocket stage and shepherding ...
Team reports major step forward in cell reprogramming
Oct 08, 2009 |
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(PhysOrg.com) -- A team of Harvard Stem Cell Institute (HSCI) researchers has made a major advance toward producing induced pluripotent stem cells, or iPS cells, that are safe enough to use in treating diseases ...
