In this work a comparative analysis of the performance of the Hartree-Fock and Kohn-Sham orbitals energies to produce reliable electronic properties is evaluated. Our results suggest that the negative of Hartree-Fock and Kohn-Sham highest occupied orbital define upper and lower limits for the experimental values of the first ionization potential. Chemical potential, hardness and polarizabilities of seventeen representative molecules have been evaluated at the Hartree-Fock and Density Functional Theory levels and a new quasi-analytic model to estimated the energy of the lowest unoccupied molecular orbital emerged from the analysis of these properties