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  2. Composition of the human body - Wikipedia

    en.wikipedia.org/wiki/Composition_of_the_human_body

    Pie charts of typical human body composition by percent of mass, and by percent of atomic composition (atomic percent) Body composition may be analyzed in various ways. This can be done in terms of the chemical elements present, or by molecular structure e.g., water , protein , fats (or lipids ), hydroxyapatite (in bones), carbohydrates (such ...

  3. Allotropy - Wikipedia

    en.wikipedia.org/wiki/Allotropy

    Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in crystalline structure.. Allotropy or allotropism (from Ancient Greek ἄλλος (allos) 'other' and τρόπος (tropos) 'manner, form') is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements.

  4. Allotropes of carbon - Wikipedia

    en.wikipedia.org/wiki/Allotropes_of_carbon

    Lonsdaleite is an allotrope sometimes called "hexagonal diamond", formed from graphite present in meteorites upon their impact on the earth. The great heat and pressure of the impact transforms the graphite into a denser form similar to diamond but retaining graphite's hexagonal crystal lattice. "Hexagonal diamond" has also been synthesized in ...

  5. Biomolecule - Wikipedia

    en.wikipedia.org/wiki/Biomolecule

    Biomolecules are an important element of living organisms. They are often endogenous, [2] i.e. produced within the organism, [3] but organisms usually also need exogenous biomolecules, for example certain nutrients, to survive. Biomolecules and their reactions are studied in biology and its subfields of biochemistry and molecular biology.

  6. Allotropes of phosphorus - Wikipedia

    en.wikipedia.org/wiki/Allotropes_of_phosphorus

    The diphosphorus allotrope (P 2) can normally be obtained only under extreme conditions (for example, from P 4 at 1100 kelvin). In 2006, the diatomic molecule was generated in homogeneous solution under normal conditions with the use of transition metal complexes (for example, tungsten and niobium). [41]

  7. Allotropes of oxygen - Wikipedia

    en.wikipedia.org/wiki/Allotropes_of_oxygen

    Triatomic oxygen (ozone, O 3) is a very reactive allotrope of oxygen that is a pale blue gas at standard temperature and pressure. Liquid and solid O 3 have a deeper blue color than ordinary O 2, and they are unstable and explosive. [5] [6] In its gas phase, ozone is destructive to materials like rubber and fabric and is damaging to lung tissue ...

  8. Graphene - Wikipedia

    en.wikipedia.org/wiki/Graphene

    It is an allotrope of carbon in the form of a plane of sp 2-bonded atoms with a molecular bond length of 0.142 nm (1.42 Å). In a graphene sheet, each atom is connected to its three nearest carbon neighbors by σ-bonds , and a delocalized π-bond , which contributes to a valence band that extends over the whole sheet.

  9. Linear acetylenic carbon - Wikipedia

    en.wikipedia.org/wiki/Linear_acetylenic_carbon

    Electron micrograph of a linear carbon chain (carbyne) between a carbon lump and Fe electrode, approximately 36 nm wide image [1]. Linear acetylenic carbon (LAC), also known as carbyne or a Linear Carbon Chain (LCC), is an allotrope of carbon that has the chemical structure (−C≡C−) n as a repeat unit, with alternating single and triple bonds.