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Conformational effects on the σ‐electron delocalization in oligosilanes are addressed by Hartree–Fock and time‐dependent density functional theory calculations (B3LYP, 6‐311G**) at MP2 optimized geometries of permethylated uniformly helical linear oligosilanes (all‐ω‐Si_nR_2n+2) up ton=16 and for backbone dihedral anglesω=55–180°. The extent of σ delocalization is judged by the partition ratio of the highest occupied molecular orbital and is reflected in the dependence of its shape and energy and of UV absorption spectra onn. The results agree with known spectra of all‐transoidloose‐helix conformers (all‐[±165]‐Si_nMe_2n+2) and reveal a transition atω≈90° from the “σ‐delocalized” limit atω=180° toward and close to the physically non‐realizable “σ‐localized” tight‐helix limitω=0 with entirely different properties. The distinction is also obtained in the Hückel Ladder H and C models of σ delocalization. An easy intuitive way to understand the origin of the two contrasting limits is to first view the linear chain as two subchains with alternating primary and vicinal interactions (σ hyperconjugation), one consisting of the odd and the other of the even σ(SiSi) bonds, and then allow the two subchains to interact by geminal interactions (σ conjugation).