Slater等根据原子结构的量子理论提出用屏蔽常数σ_i表示某自旋轨道i上的电子(简称i电子)所受其它各电子的排斥作用相当于抵消掉若干个核电荷的吸引作用,并通过对各元素的X-射线和光学光谱项的理论分析确定了j-电子对i-电子的屏蔽常数σ_(ji)的一些规律。徐光宪等曾对其加以改进。应用这些规律可判断多电子原子价轨道能级次序,并成功地从理论上阐明由实验确定的电子分层排布规律,使元素周期律从理论上得到发展。“屏蔽”效应主要是表达电子相互排斥的效应。把传统的“钻穿”效应的概念略加改进后,可使其主要表达核对电子吸引作用的效应。为此,定义i-电子轨道半径参量r_(p,i)的概念, According to the quantum theory of the atomic structure, Slater et al. Proposed that the shielding constant σ_i indicates that the repulsion of other electrons on a spin orbit i is equivalent to offsetting the attracting effect of several nuclear charges, The theoretical analysis of the X-ray and optical spectra of each element determines some of the rules for the j-electron shielding constant σ_ (ji) for i-electrons. Xu Guangxian and other had to be improved. Applying these rules, we can determine the order of the electron valence orbit energy levels and successfully explain the theoretically determined rule of the electron stratification and arrangement, which makes the periodic law of the elements develop theoretically. The “masking” effect is mainly the effect of expressing the mutual exclusion of electrons. A slight improvement on the concept of the traditional “drilled through” effect can be made to mainly express the effect of checking electronic attraction. To this end, the definition of i-electron orbital radius parameter r_ (p, i)