Atomic Radii for Depicting Atoms in a Molecule II: The Effective Atomic Radius and van der Waals Radius from 1H to 54Xe

We consider the effective atomic radius (rear), defined as the distance from the nucleus at which the magnitude of the electric field is that in He at one half of the equilibrium bond length of He2, for atoms from H to Xe. The value of rear accurately reflects the electronic configuration; for example, the effective radius shortens smoothly from B 2s22p1 to Ne 2s22p6, in contrast to the van der Waals radius (rvdW) which behaves irregularly with atomic number from B to Ne. The valence radii (rval) are also defined and discussed. Values of rear and rval are used to depict the electron charge distribution of the homonuclear diatomic molecules of groups 15, 18, and transition-metal atoms, and provide insight into the characteristics of these molecules.