Molecule

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molecule : the smallest particle of a substance that retains all the properties of the substance and is composed of one or more atoms — Webster

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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

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Science

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

App: Molecules (Theodore Gray)

Merck Index Online – Chemicals, Drugs and Biologicals (Royal Society of Chemistry)
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MathMol: An introductory site for Molecular Modeling (NYU)

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Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.

  • 'Cyborg soil' reveals the secret microbial...
    on July 23, 2021 at 2:50 pm

    Dig a teaspoon into your nearest clump of soil, and what you'll emerge with will contain more microorganisms than there are people on Earth. We know this from lab studies that analyze samples of earth scooped from the microbial wild to determine which forms of microscopic life exist in the world beneath our feet.

  • Autonomous self-healing seen in piezoelectric...
    on July 23, 2021 at 2:40 pm

    A team of researchers from the Indian Institute of Science Education and Research in Kolkata, the Indian Institute of Technology Kharagpur and RWTH Aachen University, has found a type of piezoelectric molecular crystal that is capable of autonomous self-healing. In their paper published in the journal Science, the group describes their work with piezoelectric molecular crystals and the crystals they grew that could heal themselves.

  • A device that cracks milk protein
    on July 23, 2021 at 2:24 pm

    After gaining world attention by 'unboiling' egg protein, Flinders University scientists have now used an Australian-made novel thin film microfluidic device to manipulate Beta-lactoglobulin (β-lactoglobulin), the major whey protein in cow, sheep and other mammal milks.

  • Hunting for TB's most vulnerable genes
    on July 23, 2021 at 2:00 pm

    Developing drugs to combat tuberculosis, or TB, can be frustrating business. A gene essential to the bacteria's lifecycle is discovered, scientists rush to develop drugs that inhibit the target, and then—disappointment. Volleys of compounds hurled at the essential gene target have little impact on microbial growth. The bacteria live on. The scientists return to the drawing board.

  • Scientists seek better understanding of Earth's...
    on July 23, 2021 at 12:40 pm

    Long-term studies of ozone and water vapor in the atmosphere of Mars could lead to better understanding of atmospheric chemistry for the Earth. A new analysis of data from ESA's Mars Express mission has revealed that our knowledge of the way these atmospheric gases interact with each other is incomplete.