It has been demonstrated that the soft Coulomb hole method is a reliable and efficient approach to calculate the electron correlation energy for atoms and molecules. In this method the perturbation operator -e(-wr2)12/r(12) is introduced, where omega determines the size of the Coulomb hole. The set of parameters for omega has been redetermined to calculate equilibrium bond distances. Calculations have been performed for 41 homo- and heteronuclear singlet diatomic molecules and ions (X (1)Sigma(+)), including atoms of the second and third periods of the periodic table. The soft Coulomb hole correlation energies are compared to the corresponding empirical correlation energies. In general, calculated equilibrium bond distances are in better agreement with the experimental values than Hartree-Fock and Moller-Plesset-2 results. With respect to Moller-Plesset-3, the soft Coulomb hole method gives slightly larger values for the average deviations, except for the homonuclear series.