Contracted Gaussian basis set of 5 zeta valence quality plus polarization functions for the atoms from H to Ar are presented. We assess the performance of the basis set comparing total HF and second order correlation energies of a sample of diatomic molecules with results obtained numerically or using basis sets reported in the literature. By fitting the directly calculated values through an extrapolation scheme, estimates of the complete basis set limits for second order correlation energy have been obtained. In addition, using some correlated methods, dissociation energies are evaluated and compared with experimental data. (c) 2006 Elsevier B.V. All rights reserved.