Wave functions obtained from a hard-core atomic model using first ionization potentials as the only parameters have been used in a numerical valence bond study of twelve diatomic molecules formed by copper, silver and gold, among themselves and with hydrogen and lithium. Only those wave functions (1s-type) without nodes in the bonding region have been found to give satisfactory agreement between calculated and observed values of interatomic distance and dissociation energy. The agreement with experiment is shown to be fair.