Electronegativity

Electronegativity is a concept that is raised by chemists as the development of the phenomenon of a permanent dipole moment caused by asymmetric molecules. Electronegativity is defined as the latent power of an atom within a molecule to attract electrons. This concept depends on theoretical structure of modern organic chemistry to interpret some properties such as: strength of acidity and alkalinity, chemical bond lengths, ionic character, volatility, solubility, redox potential, hydrogen bond strength, and others.

Several methods have been proposed to set the scale of electronegativity atoms but the most widely used is the Pauling scale which This scale, based on thermodynamic data. Pauling think that is feasible to expect the energy of a bond AB from the arithmetic average bond energy molecular symmetry A-A and B-B. Of course this can be met if the atoms A and B quite similar.

If the electronegativity of A and B are different then the electron density of covalent bonds will not symmetric, but higher near atomic berelektronegativitas more great that in this atomic parial generated negative charge, and on the other atoms generated positive charge. 

Therefore, the covalent bond containing ionic character, and pull Coulombik between opposite charges create a stronger bond than if in a pure covalent bond. Therefore, the observed bond energy EAB will be more greater than the arithmetic average of A2 and B2 binding energy. To calculate the difference This, Pauling using equation:

This equation is used to compile the relative electronegativity scale. Need Note that DAB is equivalent to the heat removed from the reaction if substances are all in a state of gas.

 

As restrictions on DAB equation, D is the extra ionic energy (extra) of the covalent bond A - B and is always positive. However, in some respects, as examples are the alkali hydride, D is calculated is negative. Pauling later suggested that if the average binding energy algebra is replaced by the geometric average, then the price of D positive for all concerned.

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Because DAB arise from differences in electronegativity of A and B, it is feasible to make the equation DAB as a function of electronegativity differences.