One advantage of the effective valence shell Hamiltonian method is that the spin-orbit coupling energies of all valence states, regardless of the number of valence electrons, are simultaneously determined with a similar accuracy from a single computation of the effective spin-orbit coupling operator. To assess the accuracy of the effective Hamiltonian method extensively, calculations are performed for the spin-orbit splittings in the valence states of fourth row diatomic monohydrides and their ions. The calculated spin-orbit splittings are generally in good agreement with known experiments or computations. Furthermore, the spin-orbit splittings of valence states, for which neither experiment nor theory is available, are predicted. (C) 2010 Elsevier B. V. All rights reserved.