Electronics & Semiconductors

Renewable energy, new perspectives for photovoltaic cells

In the future, photovoltaic cells could be 'worn' over clothes, placed on cars or even on beach umbrellas. These are just some of the possible developments from a study published in Nature Communications by researchers at ...

Energy & Green Tech

Turning seawater into stored energy

Afew years ago, Harvard chemist Daniel Nocera, along with collaborators from Harvard Medical School, created a system that uses sunlight to split water molecules and combine them with carbon dioxide from air to produce renewable ...


Researchers create a highly sensitive biohybrid olfactory sensor

A keen sense of smell is a powerful ability shared by many organisms. However, it has proven difficult to replicate by artificial means. Researchers combined biological and engineered elements to create what is known as a ...

Energy & Green Tech

The continuing quest to find a better battery

Ten years ago, if you needed a battery for something more than a flashlight or an alarm clock, your options were pretty limited. Lithium-ion batteries had found their way into consumer electronics in the 1990s, and researchers ...

Electronics & Semiconductors

A molecular shift register that can be controlled by external charges

In recent years, electronics engineers have been trying to create molecular-scale electronics, new types of devices that use single molecules. In order for these devices to work, however, scientists first need to identify ...

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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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