Wang Zhen-Ling, Hu Han-Shi, von Szentpály László, Stoll Hermann, Fritzsche Stephan, Pyykkö Pekka, Schwarz W H Eugen, Li Jun
Department of Chemistry & Key Laboratory of Organic Optoelectronics, and Molecular Engineering of the Ministry of Education, Tsinghua University, Beijing, 100084, P.R. China.
Institut für Theoretische Chemie, Universität Stuttgart, Stuttgart, 70550, Germany.
Chemistry. 2020 Dec 1;26(67):15558-15564. doi: 10.1002/chem.202003920. Epub 2020 Nov 16.
The Periodic Table, and the unique chemical behavior of the first element in a column (group), were discovered simultaneously one and a half centuries ago. Half a century ago, this unique chemistry of the light homologs was correlated to the then available atomic orbital (AO) radii. The radially nodeless 1s, 2p, 3d, 4f valence AOs are particularly compact. The similarity of r(2s)≈r(2p) leads to pronounced sp-hybrid bonding of the light p-block elements, whereas the heavier p elements with n≥3 exhibit r(ns) ≪ r(np) of approximately -20 to -30 %. Herein, a comprehensive physical explanation is presented in terms of kinetic radial and angular, as well as potential nuclear-attraction and electron-screening effects. For hydrogen-like atoms and all inner shells of the heavy atoms, r(2s) ≫ r(2p) by +20 to +30 %, whereas r(3s)≳r(3p)≳r(3d), since in Coulomb potentials radial motion is more radial orbital expanding than angular motion. However, the screening of nuclear attraction by inner core shells is more efficient for s than for p valence shells. The uniqueness of the 2p AO is explained by this differential shielding. Thereby, the present work paves the way for future physical explanations of the 3d, 4f, and 5g cases.
元素周期表以及一列（族）中第一种元素独特的化学行为，是在一个半世纪前同时被发现的。半个世纪前，轻同系物的这种独特化学性质与当时可得的原子轨道（AO）半径相关联。径向无节点的1s、2p、3d、4f价轨道特别紧凑。r(2s)≈r(2p)的相似性导致轻p区元素形成明显的sp杂化键，而n≥3的较重p区元素表现出r(ns) ≪ r(np)，大约相差 -20% 到 -30%。在此，从动力学径向和角向以及势核吸引和电子屏蔽效应方面给出了一个全面的物理解释。对于类氢原子和重原子的所有内壳层，r(2s) 比 r(2p) 大 +20% 到 +30%，而r(3s)≳r(3p)≳r(3d)，因为在库仑势中，径向运动比角向运动更能使轨道径向扩展。然而，内芯壳层对核吸引的屏蔽对s价壳层比重价壳层更有效。2p轨道的独特性通过这种差异屏蔽来解释。由此，本工作为未来对3d、4f和5g情况的物理解释铺平了道路。
