Shared-pair link

Shared-pair link. That type of chemical binding in which the electron systems of the participating atoms merge without complete transfer of charge from one atom to another a covalent or un-ionized bond the opposite of ionic bond. 

A single shared pair of electrons is called a single bond. Two electron pairs shared between two atoms constitute a double bond, and three shared electron pairs constitute a triple bond. A double bond, such as C 0, is written C=0 in a Lewis structure. Similarly, a triple bond, such as C C, is written G C. Double and triple bonds are collectively called multiple bonds. The bond order is the number of bonds that link a specific pair of atoms. The bond order in H, is 1 in the group C=0, it is 2 and, for O C in a molecule such as ethyne, C2H2, the bond order is 3. 

A reference picture for the bonding between atoms is indeed related to the electrons which are needed for an atom to obtain the electron configuration of the next noble gas in the Periodic Table. In the specific case of a pair of electrons shared by two atoms, each atom gains one electron in its valence shell. The energy decrease of the shared electron pair links the two atoms (the two centres) and we speak of a two electron-two centre bond (2e, 2c bond). 

High pressure and temperature are required to produce the compounds MCr03, e.g. BaCr03, which exists as several polytypes.13octahedrally coordinated in these compounds,1306 the structure consisting of pairs of face-sharing octahedra linked to other pairs by sharing comers. The Cr—Cr distances are ca. 2.6 A. 

Many more structures are known in which vertices and edges of octahedral coordination groups are shared, and models of several of them are described in MSIC. A relatively simple example is the AX3 framework formed from edge-sharing pairs of octahedra which are further linked to form the 3D framework of Fig. 5.33. This framework is the basis of the structure of one form of KSb03 and of KBiOj,... 

Na2HAs04.7 H2O. This hydrate contains a unique chain of composition Na2(H20)7 (Fig. 15.12) formed from face-sharing pairs of Na(H20)6 octahedra which also share two terminal edges. The chains are cross-linked at intervals by 0—H—0 bonds, and the As03(0H) ions are accommodated between the chains. T tere is the same H2O M ratio in NaOH. 3 H2O, in which there is complete hydration of the cations as in the arsenate. 

Double bond A link between atoms formed by two shared pairs of electrons... 

All next-nearest neighbors i and j , linking them only if the 2-tuple (q,/ ) = (1,3). By next-nearest neighbor we mean those pairs which are themselves unlinked but which share at least one other linked neighbor a,g), h,r) and w,y), for example, are all next-nearest neighbors at t = l. For c and g we find... 

Bonded atoms can share more than one electron pair. A double bond occurs when bonded atoms share two electron pairs in a triple bond, three pairs of electrons are shared. In ethylene (Q2H4) and acetylene (QHJ, the carbon atoms are linked by a double bond and triple bond, respectively. Using two parallel lines to represent a double bond and three for a triple bond, we write the structures of these molecules as... 

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