Heavy Element π Donation Is Not Less Effective

The inherent stabilizing effects of lone pair substituents from the first five rows of the periodic table on carbocations depend primarily on the group rather than on the period, judging from high‐level ab initio computations (QCISD(T)/DZ + + PP// MP2(fc)/DZ+P). When planarity is imposed on the pnictogen compounds, the stabilization energies from group 15 substituents are almost constant (ca. 95 kcal mol−1 from N to Sb, based on CH ) and exceed the stabilization energies of chalcogens (60‐66 kcal mol−1, O −1, F