Medical research

Scientists discover potential cause of Alzheimer's disease

Prevailing theories posit plaques in the brain cause Alzheimer's disease. New UC Riverside research instead points to cells' slowing ability to clean themselves as the likely cause of unhealthy brain buildup.

Diseases, Conditions, Syndromes

Researchers cure drug-resistant infections without antibiotics

Biochemists, microbiologists, drug discovery experts and infectious disease doctors have teamed up in a new study that shows antibiotics are not always necessary to cure sepsis in mice. Instead of killing causative bacteria ...

Diseases, Conditions, Syndromes

How one of the oldest natural insecticides keeps mosquitoes away

With mosquito season upon us, people are stocking up on repellents to prevent itchy bites. Bug repellents are important because they don't just protect against the buzzing, blood-sucking little pests—they also safeguard ...

Medical research

How exercise reduces belly fat in humans

Some of you may have made a New Year's resolution to hit the gym to tackle that annoying belly fat. But have you ever wondered how physical activity produces this desired effect? A signaling molecule called interleukin-6 ...

Immunology

Fever alters immune cells so they can better reach infections

Fever is known to help power up our immune cells, and scientists in Shanghai have new evidence explaining how. They found in mice that fever alters surface proteins on immune cells like lymphocytes to make them better able ...

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Molecule

A 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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