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  2. Molecule - Wikipedia

    en.wikipedia.org/wiki/Molecule

    A molecule may be homonuclear, that is, it consists of atoms of one chemical element, e.g. two atoms in the oxygen molecule (O 2); or it may be heteronuclear, a chemical compound composed of more than one element, e.g. water (two hydrogen atoms and one oxygen atom; H 2 O).

  3. Butyl group - Wikipedia

    en.wikipedia.org/wiki/Butyl_group

    Alkyl radicals are often considered as a series, a progression sequenced by the number of carbon atoms involved. In that progression, Butyl (containing 4 carbon atoms) is the fourth, and the last with preferred IUPAC name derived from its history. The word "butyl" is derived from butyric acid, a four-carbon carboxylic acid found in rancid ...

  4. Carbon group - Wikipedia

    en.wikipedia.org/wiki/Carbon_group

    Among main group (groups 1, 2, 13–17) alkyl derivatives QR n, where n is the standard bonding number for Q (see lambda convention), the group 14 derivatives QR 4 are notable in being electron-precise: they are neither electron-deficient (having fewer electrons than an octet and tending to be Lewis acidic at Q and usually existing as ...

  5. Atomicity (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Atomicity_(chemistry)

    Atomicity is the total number of atoms present in a molecule of an element. For example, each molecule of oxygen (O 2) is composed of two oxygen atoms. Therefore, the atomicity of oxygen is 2. [1] In older contexts, atomicity is sometimes equivalent to valency. Some authors also use the term to refer to the maximum number of valencies observed ...

  6. List of chemical elements - Wikipedia

    en.wikipedia.org/wiki/List_of_chemical_elements

    118 chemical elements have been identified and named officially by IUPAC.A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z).

  7. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but isotopes exist with no neutrons (hydrogen-1, by far the most common form, [57] also called protium), one neutron , two neutrons and more than two neutrons.

  8. Group (periodic table) - Wikipedia

    en.wikipedia.org/wiki/Group_(periodic_table)

    a Group 1 is composed of hydrogen (H) and the alkali metals. Elements of the group have one s-electron in the outer electron shell. Hydrogen is not considered to be an alkali metal as it is not a metal, though it is more analogous to them than any other group. This makes the group somewhat exceptional.

  9. Tetrahedral molecular geometry - Wikipedia

    en.wikipedia.org/wiki/Tetrahedral_molecular_geometry

    An inorganic example is tetraphosphorus (P 4) which has four phosphorus atoms at the vertices of a tetrahedron and each bonded to the other three. An organic example is tetrahedrane ( C 4 H 4 ) with four carbon atoms each bonded to one hydrogen and the other three carbons.