The formations, binding energies and monomer dipole moments of small water cluster systems (H₂O)_n with n = 1-12, have been investigated by the density functional calculations using B3LYP/6-311++(2d,2p) level theory. A new method based on reactivity indices from Fukui functions has been introduced to generate the initial structures. Constant adding one by one water molecule from monomer to the cluster systems (hydration reactions) have transformed the cluster shapes by following formation order: linear (n = 2), cyclic planar (n = 3-6) and 3-dimensional (n = 7-12) ones. The average binding energies of small water cluster systems have converged asymptotically to the intermolecular binding of bulk water, concerning the local binding energy fluctuation effects on the average binding energy trend. Based on total electronic energies, zero point energies and optimized transition structures energies (activation energies) analysis, we have predicted that the cyclic planar is the most stable hexamer formation to compete with the cage and the book ones. Considering the monomer dipole moment calculations with regard to the experimental data references, we have discovered new findings which have not clarified yet before, that the smallest piece of ice water is the cyclic tetramer (n = 4) and the cage hexamer is the smallest stable liquid formation. [DOI: 10.1380/ejssnt.2009.871]