Trends in carbon 1s ionization energies for the linear alkanes have been investigated using third-generation synchrotron radiation. The study comprises CH4, C2H6, C3H8, C4H10, C5H12, C6H14, and C8H18. Both inter- and intramolecular shifts in ionization energy have been determined from gas-phase spectra and ab initio calculations. The shifts are decomposed into initial-state and final-state contributions and are shown to relate to the fundamental chemical properties of group electronegativity and polarizability. By extrapolation, we predict C1s spectra of larger n-alkanes, converging toward isolated strands of polyethylene.