The successive H2O binding energies, computed using density functional theory (DFT), are in good agreement with experiment. The bonding is electrostatic (charge-dipole) in origin for ah systems. The structures are therefore determined mostly by metal-ligand and ligand-ligand repulsion. The computed structure for FeH2O+ is C-2 upsilon, where sp hybridization is important in reducing the Fe-H2O repulsion. Fe(H2O)(2)(+) has D-2d symmetry where sd(sigma) hybridization is the primary factor leading to the Linear O-Fe-O geometry. The bonding in Fe(H2O)(3)(+) and Fe(H2O)(4)(+) is very complex because ligand-ligand and metal-ligand repulsion, both for the in-plane and out-of-plane water lone-pair orbitals, are important.