Electronegativity, Mendeleev number, Miedema parameters

3 Electronegativity, Mendeleev number, Miedema parameters. A few semi-empirical parameters and scales which are useful as reference data in the systematic description (or even prediction) of the alloying behaviour of the different metals will be presented here also as an introduction to the following paragraphs. The closely related basic concepts of chemical periodicity and electron configurations will be reminded in Chapter 4. 

Electronegativity and the so-called Mendeleev number are two parameters, basically empirical at least in their initial definitions, which, however, proved to be very 

The Miedema s parameters and the Miedema model and formula proved to be useful in an approximate evaluation of the formation enthalpy of alloys, in the estimate of the formation capability of intermetallic compounds, etc. 

In this equation //A and r/B are values of electronegativity assigned to atoms A and B. In the original formulation of the electronegativity scale, the electron volt was used as the unit of energy this use accounts for the approximate factor 23 in the equation. (leV = 1.60217653(14) 10 19J,Avogadro number 6.0221415(10) 1023mol 1). 

On the basis of this equation, systematically considering all the available thermochemical data and arbitrarily assigning to the most electronegative element, fluorine, a value of about 4, Pauling was able to prepare a complete electronegativity scale. This is shown in Table 2.1. 

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In the same chapter (Chapter 5), as an introduction to the paragraphs dedicated to the various groups of metals, the values relevant to a number of elementary properties have been collected. These are atomic properties (such as metallic and ionic radii, ionization energies, electronegativities, Mendeleev number, chemical scale, Miedema parameters, etc.), crystal structure and lattice parameters data of the allotropes of the elements, and selected thermodynamic data (melting and boiling temperatures and enthalpies, etc.). All these data indeed represent reference values in the discussion of the alloying behaviour of the elements. 

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