According to the Kolmogorov-Smirnov analysis in Sec. II of the ESI † , the functional groups only indirectly influence the magnitude of the polarizability in a given molecule, whereas the atomic composition is a crucial factor for the determination of the polarizability. This finding is also in line with the fact that a good correlation is achieved between the first-order atomic additive model and the reference DFT data shown in Fig. . The ∆E HL and α values for a set of two constitution isomers, namely with the chemical formula C 4 H 8 O (including aldehydes, dialkyl ethers, enol ethers, as well as primary and secondary alcohols) and C 4 H 9 N (including carbonitriles and primary/secondary aliphatic amines) is also presented in Figs. , showing a narrow polarizability distribution. These results are another clear evidence that α, to a reasonable approximation, is independent of the actual chemical arrangement of the atoms in the molecule but it mainly depends on the total number of atom-types.