This article analyzes how the individual structural elements of surfactant molecules affect surface properties, in particular, the point of reference defined by the limiting surface tension at the aqueous cmc, gamma(cmc). Particular emphasis is given to how the chemical nature and structure of the hydrophobic tails influence gamma(cmc). By comparing the three different classes of surfactants, fluorocarbon, silicone, and hydrocarbon, a generalized surface packing index is introduced which is independent of the chemical nature of the surfactants. This parameter phi(cmc) represents the volume fraction of surfactant chain fragments in a surface film at the aqueous cmc. It is shown that gamma(cmc) is a useful index for understanding the limiting surface tension of surfactants and can be useful for designing new superefficient surfactants.