Document Type : Research Paper
Chemical hardness () and absolute electronegativity () have important applications in chemistry. In
the conceptual Density Functional theory (DFT), these concepts has been associated with electronic
energy and the relationship with ionization energy (I) and electron affinity (A) of these concepts has
been given. In this study, graphical method was used in order to see the relationship with the atomic
number (Z) of chemical hardness and absolute electronegativity in isoelectronic series. These series
was considered because all members of an isoelectronic series have the same shielding constant.
Chemical hardness and electronegativity equations depending on atomic number were obtained from
graphs of =f(Z) and =f(Z) for isoelectronic series that contain electron from 1 to 20. Ionization
energy and electron affinity equations were obtained making use from the chemical hardness and
electronegativity equations. In the last stage, the relationship with the number of electron of
coefficients in the ionization energy and electron affinity equations was examined. As a result, new
equations consistent with experimental results that depending on atomic number and number of
electron were obtained.