Abstract: On basis of ab initio quantum chemical calculations formulas for calculating screening constants σ_(ji) and orbital radius parameters r_(p,i) (used for expressing the penetrating effect) have been established. The rules of penetrating and screening effects have been modified: (1) For 3d and 4d transition elements the (n-1)d orbitals penetrate more deeply than the ns, where n denotes the principal quantum number of the outermost shell; for RE atoms 4f penetrates more deeply than 6s. (2) The screening constants between electrons in the same sub-shell is rather large, 0.65-0.7. (3) The screening constants of the outermost shell electron to that of the next out are not negligible, 0.3-0.4. Some difficulties in the theory of the atomic structure principle may thus be overcome.

Key words: Penetrating effects, Screening effects, ab initio, Transition elements, Rare-earth elements