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
First Pump-Probe Experiment at Linac Coherent Light Source Completed
11 hours ago |
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(PhysOrg.com) -- The first experiment using the Linac Coherent Light Source to illuminate molecules via a "pump-probe" technique has been completed by an international team of more than 30 scientists from ...
First live targeting of tumors with RNA-based technology
17 hours ago |
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(PhysOrg.com) -- Finding and treating a tumor without disturbing normal tissue presents challenges - sometimes the most effective therapies can be invasive and harsh.
Multiferroic compounds used to produce smaller and cheaper digital memories
Nov 27, 2009 |
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(PhysOrg.com) -- Is it possible to make even more compact digital memories for portable electronic devices and which consume even less energy? A team of French researchers has recently demonstrated that it ...
Herschel takes a peek at the ingredients of the galaxies
Nov 27, 2009 |
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(PhysOrg.com) -- The European Space Agency has today released spectacular new observations from the Herschel Space Observatory, including the UK-led SPIRE instrument. Spectrometers on board all three Hershel ...
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Ice Cold: Cooler Than Being Cool
Nov 24, 2009 |
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(PhysOrg.com) -- Water expands when it freezes. Anyone who has ever left a can of soda or bottle of water in the freezer too long has witnessed this first hand. So how do plants and animals survive severe ...
Stroke and heart disease trigger revealed in new research
12 hours ago |
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Scientists have identified the trigger that leads to the arteries becoming damaged in the disease atherosclerosis, which causes heart attacks and strokes, in research published today in the journal Circulation. The author ...
Two molecules affecting brain plasticity
Medicine & Health / Neuroscience
Nov 25, 2009 |
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(PhysOrg.com) -- You wouldn't want a car with no brakes. It turns out that the developing brain needs them, too.
Microscopy reveals structure of calcite shells
11 hours ago |
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(PhysOrg.com) -- Lara Estroff and colleagues have taken a deep, detailed look at the way lab-created calcite crystals, similar to those found in nature, grow in tandem with proteins and other large molecules.
It takes two to infect: Structural biologists shed light on mechanism of invasion protein
16 hours ago |
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Bacteria are quite creative when infecting the human organism. They invade cells, migrate through the body, avoid an immune response and misuse processes of the host cell for their own purposes. To this end every bacterium ...
Scientists reveal malaria parasites' tactics for outwitting our immune systems
12 hours ago |
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Malaria parasites are able to disguise themselves to avoid the host's immune system, according to research funded by the Wellcome Trust and published today in the journal Proceedings of the National Academy of ...
A challenge to improve Nuclear Magnetic Resonance for structural biology
22 hours ago |
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(PhysOrg.com) -- In structural biology, the only technique available to predict the three dimensional structure of large complex molecules in solution, such as proteins and DNA, is NMR spectroscopy. To catalyze improvements ...
Study describes new tool in the fight against autoimmune diseases, blood cancers
11 hours ago |
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A study led by a Scripps Research Institute scientist describes a new, highly pragmatic approach to the identification of molecules that prevent a specific type of immune cells from attacking their host. The findings add ...
Scientists find clue to mystery of biological clock
Medicine & Health / Neuroscience
16 hours ago |
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How does our biological system know that it is supposed to operate on a 24-hour cycle? Scientists at the Hebrew University of Jerusalem have discovered that a tiny molecule holds the clue to the mystery.
Fast, easy, and highly sensitive arsenic detection with gold nanoparticles
Nanotechnology / Nanomaterials
Nov 25, 2009 |
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(PhysOrg.com) -- Mention of arsenic poisoning usually brings to mind underhanded murder. However, the danger of arsenic poisoning from contaminated drinking water is far greater. Low concentrations of arsenic are found in ...
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