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.
For more information about Molecule, read the full article at
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News tagged with molecules
Newly explored bacteria reveal some huge RNA surprises
14 hours ago |
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(PhysOrg.com) -- Yale University researchers have found very large RNA structures within previously unstudied bacteria that appear crucial to basic biological functions such as helping viruses infect cells ...
Stick and slide: Computer simulation advances understanding of molecular motors
16 hours ago |
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A new study reveals how molecular motors that power important subcellular movements can generate cyclical motion. The research, published by Cell Press in the December issue of the Biophysical Journal, opens a new door t ...
High urea levels in chronic kidney failure might be toxic after all
Dec 02, 2009 |
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It is thought that the elevated levels of urea (the byproduct of protein breakdown that is excreted in the urine) in patients with end-stage kidney failure are not particularly toxic.
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Researchers Identify Key Molecules in Photosynthesis
22 hours ago |
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(PhysOrg.com) -- Chemistry professor Harry Frank led an international group of researchers that identified the molecules in algae which direct the organisms to convert sunlight into oxygen. The findings may ...
A little magic provides an atomic-level look at bone
Chemistry / Analytical Chemistry
13 hours ago |
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(PhysOrg.com) -- A new study using solid-state NMR spectroscopy to analyze intact bone paves the way for atomic-level explorations of how disease and aging affect bone. The research by scientists at the University of Michigan ...
Human Mdm2: A new molecular link to late-stage metastatic breast cancer
22 hours ago |
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A large proportion of late-stage breast cancers that have spread to other parts of the body (metastatic breast cancers) are characterized by overexpression of the protein Mdm2.
Discovery makes brain tumor cells more responsive to radiation
17 hours ago |
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Duke University Medical Center researchers have figured out how stem cells in the malignant brain cancer glioma may be better able to resist radiation therapy. And using a drug to block a particular signaling pathway in these ...
Nervy research: Researchers take initial look at ion channels in a model system
18 hours ago |
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Before one of your muscles can twitch, before the thought telling it to flex can race down your nerve, a tiny floodgate of sorts -- called an ion channel -- must open in the surface of each cell in these organs ...
A light touch: Iron complexes as efficient catalysts for the light-driven extraction of hydrogen from water
20 hours ago |
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(PhysOrg.com) -- Hydrogen is a promising alternative energy carrier that can be efficiently converted into electrical energy in fuel cells. One hurdle to the introduction of sustainable hydrogen technology is the fact that ...
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