Hydrogen a special one-s-valence-electron atom

The solid in which hydrogen bonding plays the most crucial role is ice. Ice forms many complex phases [6] in its ordinary phase called Ih, the H2O molecules are placed so that the O atoms occupy the sites of a wurtzite lattice (see Fig. 1.5), while the H atoms are along lines that join O atoms [7]. There are two H atoms attached to each O atom by short covalent bonds (of length 1.00 A), while the distance between O atoms is 2.75 A. There is one H atom along each line joining two O atoms. The 

Within the atomic orbital picture discussed earlier for solids with 5 and p electrons, we can construct a simple argument to rationalize hydrogen bonding in the case of ice. The O atom has six valence electrons in its 5 and p shells and therefore needs two more electrons to complete its electronic structure. The two H atoms that are attached to it to form the water molecule provide these two extra electrons, at the cost of an anisotropic bonding arrangement (a completed electronic shell should be isotropic, as in the case of Ne which has two more electrons than O). The cores of the H atoms (the protons), having lost their electrons to O, experience a Coulomb repulsion. The most favorable structure for the molecule which optimizes this repulsion would be to place the two H atoms in diametrically opposite positions relative to the O atom, but this would involve only one p orbital of the O atom to which both H atoms would bond. This is an unfavorable situation as far as formation of covalent bonds is concerned, because it is not possible to 

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