Electronegativity of Atoms-in-Molecules

Elinze, J. 1999. The concept of electronegativity of atoms in molecules. In Pauling s Legacy Modem Modelling of the Chemical Bond, chap. 7, edited by Z. B. Maksic and W. J. OrvUle-Thomas, 189-212. Amsterdam, The Netherlands Elsevier. 

Concept of Electronegativity Table 2.17 Thermochemical electronegativities of atoms in molecules x(H) = 2.2... 

The average value of the equalized electronegativity of atoms in molecule can be obtained as ... 

The direct formation of a binary hydride EH from the elemental substances is usually favoured thermodynamically if E is much lower, or much higher, in electronegativity than H. Thus, for example, the free energies of formation AG of LiH and HC1 are respectively —68 and -95 kJ mol-1. In the case of HC1, it can be predicted from the relevant bond energies - rationalised in terms of Pauling s derivation of electronegativities - that the formation of HCl(g) from the elemental substances should be exothermic. Further, entropy considerations will favour the randomisation of atoms in molecules. For the reaction ... 

Engl. TransL), 296, 440 (1987). Scheme for the Calculation of the Electronegativities of Atoms in a Molecule in the Framework of Sanderson s Principle. 

A molecule is polar if its centers of positive and negative charges do not coincide. A polar covalent molecule has at least one polar covalent bond. An imderstanding of the concept of electronegativity, the relative electron-attracting power of atoms in molecules, helps us to assess the polarity of a bond. 

There is, of course, a strong correlation between AVEE and electronegativity. As shown for a few atoms in Table 2, multiplying AVEE values by 1.8 yields numbers very close to electronegativity values. For historical reasons, most chemists use electronegativity values to estimate the electron drawing power of atoms in molecules. 

Table 2.21 Geometrical electronegativities of atoms in the group valences, in molecules upper lines) and crystals (lower lines)...

Table 2.22 Recommended values of electronegativities for atoms in molecules...

Binary covalent compounds are named using the name of the less electronegative element first, followed by the stem plus -ide of the more electronegative element. Greek prefixes are used to represent the number of each type of atom in molecules of the compounds. Ionic compounds that contain a metal ion (or ammonium ion) plus a polyatomic ion are named by first naming the metal (or ammonium ion) followed by the name of the polyatomic ion. 

Alternatively, one may consider the so called geometrical mean of atoms-in-molecule electronegativity, namely through the relationships (Parr Bartolotti, 1982)... 

Putz, M. V. (2011b). On relationship between electronic sharing in bonding and electronegativity equalization of atoms in molecules. Int J. Chem. Model. 3(4), 371-384. 

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