ABSTRACT
Hardness is one of the important periodic descriptors used by scientists to correlate the physicochemical properties of atoms, molecules, and condensed phases of matter. Fundamentally, chemical hardness resists the deformation of the electron cloud of the atoms, ions, or molecules under perturbation. The concept of electronegativity and hardness is conceived from electrostatic attraction of nucleus on an electron of the periphery of atom. Electronegativity has already been defined in terms of energy and force concept as well. Though a number of researchers have defined the atomic hardness in terms of energy concept, the force model for hardness is still unexplored. Since the commonality of atomic hardness and atomic electronegativity is a well-established fact, we have defined the hardness as force model in this venture. As the atomic hardness is a force exerted by the screened nucleus on an electron at the periphery of an atom, the following ansatz is proposed to compute global hardness of periodic table, η = a (Zeff e 2/r 2) + b; which is 32used for computing hardness of 103 elements of the periodic table, where a and b represent regression coefficients. We have used absolute radii (r) computed by Chakraborty et al. in the above equation. The new scale satisfies all the sine qua non of a scale of atomic hardness. A new electronic structure principle, namely, the principle of hardness equalization principle, is also proposed in the force model. Our data successfully establish hardness equalization principle.
