These are organized by a classification scheme developed exclusively for Cosma. More…
molecule : the smallest particle of a substance that retains all the properties of the substance and is composed of one or more atoms — Webster
Molecule is an electrically neutral group of two or more atoms held together by chemical bonds. A molecule may be homonuclear, that is, it consists of atoms of one chemical element, as with oxygen (O2); or it may be heteronuclear, a chemical compound composed of more than one element, as with water (H2O). Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are generally not considered single molecules.
Molecules as components of matter are common in organic substances (and therefore biochemistry). They also make up most of the oceans and atmosphere. However, the majority of familiar solid substances on Earth, including most of the minerals that make up the crust, mantle, and core of the Earth, contain many chemical bonds, but are not made of identifiable molecules. Also, 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, quartz, or sodium chloride). The theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding, which means that solid metals are also not made of molecules. In glasses (solids that exist in a vitreous disordered state), atoms may also be held together by chemical bonds with no presence of any definable molecule, nor any of the regularity of repeating units that characterizes crystals. — Wikipedia
Molecular physics is the study of the physical properties of molecules, the chemical bonds between atoms as well as the molecular dynamics. Its most important experimental techniques are the various types of spectroscopy; scattering is also used. The field is closely related to atomic physics and overlaps greatly with theoretical chemistry, physical chemistry and chemical physics.
In addition to the electronic excitation states which are known from atoms, molecules exhibit rotational and vibrational modes whose energy levels are quantized. The smallest energy differences exist between different rotational states: pure rotational spectra are in the far infrared region (about 30 – 150 µm wavelength) of the electromagnetic spectrum. Vibrational spectra are in the near infrared (about 1 – 5 µm) and spectra resulting from electronic transitions are mostly in the visible and ultraviolet regions. From measuring rotational and vibrational spectra properties of molecules like the distance between the nuclei can be specifically calculated.
One important aspect of molecular physics is that the essential atomic orbital theory in the field of atomic physics expands to the molecular orbital theory. — Wikipedia
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Shedding light on the reaction mechanism of PUVA...
on August 20, 2019 at 3:59 pm
The term "PUVA' stands for 'psoralen' and 'UV-A radiation.' Psoralens are natural plant-based compounds that can be extracted from umbelliferous plants such as giant hogweeds. Plant extracts containing psoralens were already used in Ancient Egypt for the treatment of skin diseases. Modern medical use began in the 1950s. From then on, they were applied for light-dependent treatment of skin diseases such as psoriasis and vitiligo. From the 1970s onwards, PUVA therapy was used to treat a type of […]
A single change at telomeres controls the ability...
on August 20, 2019 at 3:14 pm
Pluripotent cells can give rise to all cells of the body, a power that researchers are eager to control because it opens the door to regenerative medicine and organ culture for transplants. But pluripotency is still a black box for science, controlled by unknown genetic (expression of genes) and epigenetic signals (biochemical marks that control gene expression like on/off switches). The Telomeres and Telomerase Group, led by Maria Blasco at the Spanish National Cancer Research Centre (CNIO), […]
Lab-on-a-chip drives search for new drugs to...
on August 20, 2019 at 2:12 pm
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Statistics plot pollution to inform policy
on August 20, 2019 at 2:09 pm
The spatial variation in different air pollution components helps identify possible targets for pollution control.
Catalysts for climate protection
on August 20, 2019 at 12:50 pm
How can we achieve the internationally agreed climate targets? The Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB makes the greenhouse gas CO2 usable as a carbon source for the chemical industry. With a patented catalyst synthesis, screening for the optimal catalyst in high throughput and combined (electro)chemical-biotechnological processes, various concepts are available to CO2 emitting industries. The platform chemical ethylene has already been successfully produced […]