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Polyatomic molecules covalent bonds

A bond between two different atoms cannot be purely covalent. Depending on the electronegativity of the bonded atoms, the bonded electron pair shifts toward one of the atoms. A vector showing the magnitude and direction of the shifting of this electron pair is known as a bond moment. In polyatomic molecules, each bond has an individual bond moment. The dipole moment ) of a molecule is the vectorial addition of such bond moments. In the cases where all the individual bond moments are zero (homoatomic molecules), the resultant dipole moment is always zero. However, the converse is not true. Because of equal and opposite values of individual bond moments, some molecules show a zero net dipole moment. As applied to coordination compounds, a dipole measurement can be of value in distinguishing between isomers of a compound, particularly between cis- and trans- isomers. A trans- isomer exhibits a low or zero dipole moment. [Pg.121]

The energy required to break the bond between two covalently bonded atoms is called the bond dissociation energy . In polyatomic molecules this quantity varies with environment. For example, ammonia has three N—H bond dissociation energies ... [Pg.47]

This chapter is devoted to the covalent bond as it exists in molecules and polyatomic ions. We consider—... [Pg.165]

These examples illustrate the principle that atoms in covalently bonded species tend to have noble-gas electronic structures. This generalization is often referred to as the octet rule. Nonmetals, except for hydrogen, achieve a noble-gas structure by sharing in an octet of electrons (eight). Hydrogen atoms, in molecules or polyatomic ions, are surrounded by a duet of electrons (two). [Pg.168]

Each atom in a polyatomic molecule completes its octet (or duplet for hydrogen) by sharing pairs of electrons with its immediate neighbors. Each shared pair counts as one covalent bond and is represented by a line between the two atoms. A Lewis structure does not portray the shape of a polyatomic molecule it simply displays which atoms are bonded together and which atoms have lone pairs. [Pg.190]

Distinguish between each of the following pairs (a) an ion and an ionic bond, (b) an ion and a free atom, (c) a covalent bond and an ionic bond, (cl) a triple bond and three single bonds on the same atom, (e) a polyatomic molecule and a polyatomic ion. [Pg.96]

Ionic compounds are made up of positively charged ions (usually metal ions) and negatively charged ions (usually non-metal ions or polyatomic anions) held together by electrostatic forces of attraction. Molecular compounds are made up of discrete units called molecules. Generally they consist of a small number of nonmetal atoms held together by covalent bonds (sharing of electrons). [Pg.44]

Small polyatomic molecules involving single covalent bonds between adjacent atoms, e.g. P4 and S8. [Pg.151]

In particular, if we have a complex that normally has n ligands when the oxidation state of the central metal is 2, but prefers (n + 2) ligands when the oxidation state is increased to (z + 2), we have the prerequisites for facile oxidative addition of a polyatomic molecule such as H2 to form two new ligands (here, hydrido ligands, H ) by breaking a covalent bond within the molecule and taking two electrons from the metal atom M (reaction 18.9). The reverse process is called reductive elimination. [Pg.399]

As in the case of a covalent bond in polyatomic molecules, a distinction should be made between the bond energy related to the bond distance and the experimentally observed dissociation energy of a hydrogen bond which includes the energy changes in the polarized systems. [Pg.260]

This section attempts a systematic classification of the covalent bonding schemes, in terms of VB theory, exhibited by atoms of the Main Group elements. The aim is to enable the reader to fit together the structure of a molecule or polyatomic ion by identifying the appropriate bonding scheme for each atom. You should try not to memorise by rote the tables in this section the material should be studied in conjunction with a text which covers the descriptive chemistry in some detail. The lists of bonding schemes are not exhaustive, but they contain the most important ones. [Pg.190]

In this section, we first discuss the bonding in two linear triatomic molecules BeH2 with only a bonds and C02 with both a and n bonds. Then we go on to treat other polyatomic molecules with the hybridization theory. Next we discuss the derivation of a self-consistent set of covalent radii for the atoms. Finally, we study the bonding and reactivity of conjugated polyenes by applying Hiickel molecular orbital theory. [Pg.99]

The essential part of non dynamical correlation energy for polyatomic molecules is the left-right electron correlation , which is concerned with the ionic-covalent balance within a given two-electron bond. Let us therefore discuss this type of correlation. [Pg.189]

A severe inconvenience of describing each bond of a polyatomic molecule by one covalent and two ionic components is that the number of VB structures grows exponentially with the size of the molecule. Coulson and Fischer [17] proposed a very elegant way to incorporate left-right correlation into a single and formally covalent VB structure of the HL type. To this end they used deformed or rather slightly delocalized orbitals as exemplified in eq 6 for H2. [Pg.191]


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See also in sourсe #XX -- [ Pg.223 , Pg.224 , Pg.225 , Pg.226 , Pg.227 , Pg.228 , Pg.229 , Pg.252 ]




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