We applied sequential atomic multipole fitting and the Gauss electric field flux theorem to calculate total molecular charge, charge distribution and charge transfer in a number of water, ion, and ion-water clusters. We have found that: (a) charge redistribution upon formation of ionic and of hydrogen bonds are similar and they are drastically different in covalent bonding; (b) polarization accounts for charge re-distribution upon formation of ionic or hydrogen bonds without invoking a charge transfer; (c) the 'charge leak' from molecular cavities, encountered in the hydration theories, is usually compensated by the electron density of the surrounding water; (d) the flux theorem provides alternative means of defining atomic radii in molecules in solution or clusters.