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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Earth first origins project seeks to replicate...
on February 15, 2019 at 3:50 pm
The evolution of planet Earth and the emergence of life during its first half-billion years are inextricably linked, with a series of planetwide transformations—formation of the ocean, evolution of the atmosphere, and the growth of crust and continents—underpinning the environmental stepping stones to life. But how, and in what order, were the ingredients for life on Earth manufactured and assembled? […]
After 90 years, a better way to measure the...
on February 15, 2019 at 2:30 pm
Researchers at the National Institute of Standards and Technology (NIST), in collaboration with the U.S. Government Publishing Office (GPO), have developed a novel, nondestructive method to rapidly measure the wood and non-wood fiber components in paper. […]
Chemical data mining boosts search for new...
on February 15, 2019 at 2:20 pm
Organic semiconductors are lightweight, flexible and easy to manufacture. But they often fail to meet expectations regarding efficiency and stability. Researchers at the Technical University of Munich (TUM) are now deploying data mining approaches to identify promising organic compounds for the electronics of the future. […]
How proteins become embedded in a cell membrane
on February 15, 2019 at 12:32 pm
Many proteins with important biological functions are embedded in a biomembrane in the cells of humans and other living organisms. But how do they get in there in the first place? Researchers in the Department of Biosystems Science and Engineering at ETH Zurich have investigated the matter. […]
Tiny particles can switch back and forth between...
on February 15, 2019 at 8:35 am
Three years ago, when Richard Robinson, associate professor of materials science and engineering, was on sabbatical at Hebrew University in Israel, he asked a graduate student to send him some nanoparticles of a specific size. […]