The stability, structure and reactivity of Na(H2O)(7), Na-2(H2O)(7), and Na-2(H2O)(10) clusters have been investigated by means of the density functional theory (DFT) method. In all cases, the 3s Na electrons are located far from their nuclei and hydrated. Particular emphasis has been placed on the influence of the water- generated electric field on sodium dimer polarization. The metal atoms hydrolysis reaction has been studied for the lone sodium atom as well as for the sodium pair; the calculated activation energies are found to be very similar in terms of magnitude. Reaction mechanisms are proposed that exhibit the role of the hydrogen bond cooperative effects in combination with proton tunneling. (C) 2003 American Institute of Physics.