A new scale of orbital radii is defined as the distance corresponding to the classical turning point of the electron in an orbital and is calculated for atomic systems using the self-interaction corrected version of the Kohn-Sham density functional theory with local spin-density approximation for the exchange and correlation. These orbital radii and different density and density derived quantities are shown to correlate very well with polarizability and other atomic properties of interest. A simple scheme is also proposed for the bond energy of a diatomic molecule in terms of the valence orbital radii and the electron density (at the boundary corresponding to the radii) of the constituent atoms. The calculated bond energies for simple heteronuclear diatomic molecules are shown to agree very well with the experimental values.