When the electron-electron interaction is explicitly considered in many-electron atoms, the average subshell radius (nl) splits into two different radii, inner radius (nl) and outer radius )>(nl), where n and l are the principal and azimuthal quantum numbers. For the 102 atoms He through Lr in their ground states, the radii (nl) and )>(nl) are systematically examined at the Hartree-Fock limit level. For a subshell nl, two exponents zeta(<)(nl)(est) and zeta(>)(nl)(est) estimated from these radii have good linear correlations with variationally determined exponents zeta(<)(nl)(var) and zeta(>)(nl)(var) of double-zeta Slater-type functions. (C) 2004 American Institute of Physics.