Spectroscopic Evaluation of the Atomic Size

A new algorithm for evaluating the atomic size is suggested by entailing the atomic spectroscopic data-the wave number. The basic tenet of the present method is (i) to convert a multi-electron atom system to a hydrogenic atom to invoke the Bohr model for the mechanism of electron transition, and (ii) to use the experimental atomic spectroscopic data of multi electron systems to determine the atomic radii. The estimated set of size data appears to satisfy the entire 'sine qua non' of sizes of atoms of the periodic table. Relativistic effect appears to have been significantly included in the suggested algorithm for evaluating the atomic radii. The express periodicity of periods and groups of periodic table exhibited by the computed atomic radii, d and f block contraction and the manifestation of the relativistic effect in the sizes of lanthanoids and actinoids etc speak volume of the efficacy of the present method in computing atomic size. Furthermore, as a validity test, the size data evaluated in the present work have been exploited to calculate some physical descriptors of the real world like equilibrium inter nuclear distances of a good number of hetero nuclear diatomics. We have noted the surprisingly close agreement between the theoretical and the experimental equilibrium inter-nuclear distances.