A model of the linear hydrogen bond has been devised which is characterized by three physical parameters of the isolated electron donor and proton donor molecules: μ A-H , the bond dipole moment; Δ I , the difference in ionization potential between that of the electron donor and the corresponding noble gas atom; and l , the length of the electron donor lone-pair of electrons. The model is able to explain dimerization energy, charge transfer, internuclear separation, directionality, stretching force constants, dimer dipole moment, and infrared intensity enhancement.