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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- Solving a crystal's structure when you've only...on January 23, 2022 at 4:00 pm
Crystals reveal the hidden geometry of molecules to the naked eye. Scientists use crystals to figure out the atomic structure of new materials, but many can't be grown large enough. Now, a team of researchers report a new technique in the January 19 issue of Nature that can discover the crystalline structure of any material.
- Fastest-ever study of how electrons respond to...on January 21, 2022 at 3:29 pm
A study of electron dynamics timed to millionths of a billionth of a second reveals the damage radiation can do on a molecular level.
- Shift work helps marine microbes share scarce...on January 21, 2022 at 3:14 pm
Though they may be small, microorganisms are the most abundant form of life in the ocean. Marine microbes are responsible for making roughly half of the organic carbon that's usable by life. Many marine microbes live near the surface, depending on energy from the sun for photosynthesis.
- First detection of exotic 'X' particles in...on January 21, 2022 at 3:14 pm
In the first millionths of a second after the Big Bang, the universe was a roiling, trillion-degree plasma of quarks and gluons—elementary particles that briefly glommed together in countless combinations before cooling and settling into more stable configurations to make the neutrons and protons of ordinary matter.
- Researchers discover crystalline zeolites in a...on January 21, 2022 at 12:16 pm
Zeolites, which are crystalline porous materials, are very widely used in the production of chemicals, fuels, materials, and other products. So far, zeolites have been made as 3D or 2D materials. This has changed with the recent discovery of crystalline zeolites in a nanotubular (1D) shape, by researchers at the Georgia Institute of Technology, Stockholm University, and Penn State University. The findings were published in the Jan. 6 issue of Science.
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