The optimized geometries, adiabatic electron affinities, and I R-active vibrational frequencies have been predicted for the long linear carbon chains HC2nH. The B3LYP density functional combined with the DZP basis set was used in this theoretical study. The computed physical properties are discussed. The predicted electron affinities form a remarkably regular sequence: 1.78 (HC12H), 2.08 (HC14H), 2.32 (HC16H), 2.53 (HC18H), 2.69 (HC20H), 2.83 (HC22H), and 2.95 eV (HC24H). The predicted structures display an alternating triple and very short single bond pattern, with the degree of bond alternation significantly less for the radical anions.