Atomic radii from electron densities.

Bond lengths for diatomic molecules are predicted from atomic radii derived from free atom one-electron densities by postulating shielding factors for their valence electrons that depend on orbital angular momentum and on the bond order. The predicted values are closer to spectroscopically measured bond lengths than those based on earlier atomic radii inferred from a wider range of structural evidence. The bond lengths predicted by the sum of the atomic radii are corrected by a reduction that allows for charge transfer and by an extension associated with exchange repulsion of the overlapping electrons in the inter-nuclear region. Both corrections are related to free atom one-electron densities.