Derivation of ionization energy and electron affinity equations using chemical hardness and absolute electronegativity in isoelectronic series

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