Machine learning & AI

Machine learning uncovers potential new TB drugs

Machine learning is a computational tool used by many biologists to analyze huge amounts of data, helping them to identify potential new drugs. MIT researchers have now incorporated a new feature into these types of machine-learning ...

Machine learning & AI

Computers excel in chemistry class

Machine learning models can rapidly and accurately estimate key chemical parameters related to molecular reactivity.

Energy & Green Tech

Oxygen breathes new life into solar cell research

Scientists in Australia and the United States have been able to 'upconvert' low energy light into high energy light, which can be captured by solar cells, in a new way, with oxygen the surprise secret ingredient. The results ...

Energy & Green Tech

Closer to a heat battery: Understanding the atomistic processes

Salts are cheap and sustainable materials that can be used to store energy (heat) over periods ranging from hours to years without loss. This works via so-called hydration-dehydration processes. Energy release (discharge) ...

Energy & Green Tech

Water vapor in the atmosphere may be prime renewable energy source

The search for renewable energy sources, which include wind, solar, hydroelectric dams, geothermal, and biomass, has preoccupied scientists and policymakers alike, due to their enormous potential in the fight against climate ...

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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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