Electronegativity equalization Allred-Rochow

Allred and Rochow chose as a measure of electronegativity of an atom the electrostatic force exerted by the effective nuclear charge eff (estimated from Slater s rules, see Box 1.6) on the valence electrons. The latter are assumed to reside at a distance from the nucleus equal to the covalent radius, r y, of the atom. Equation 1.36 gives the method of calculating values of the Allred-Rochow electronegativity, X... 

PRINCIPLE ENll (of Allred-Rochow) The electronegativity of an atom is given by the attraction force between the shielded nucleus and the electron found at a distance equal with the covalent radius and is expressed as follows ... 

The now generally accepted scale of electronegativity was derived by Allred and Rochow and is known by their names. It is based on the concept that the electronegativity of an element is related to the force of attraction experienced by an electron at a distance from the nucleus equal to the covalent radius of the particular atom. 

Small size favors hardness, other things being equal. Early consideration of hard and soft acids and bases did not go far beyond this conclusion. Until the direct relation between electronegativity and hardness was discovered, the atomic radius was associated with electronegativity rather than with hardness. Gordy (X oc Z/r [9]) and Allred and Rochow (x oc Z/r [10]) and Sanderson x ionic radius into their electronegativity... 

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