Each ice molecule is V-shaped with an angle of 109 degrees between the legs. Ice molecules are bound together in an open lattice and form puckered layers with hexagonal symmetry. Each molecule is surrounded by its four nearest neighbors, so that each group has one molecule at the center and the other four at the corners of a tetrahedron, all at the same distance away. The molecules are held in place mainly by electrostatic attraction between the positive charge of the hydrogen atom and the negative electrons of the neighboring oxygen atom. This is called a hydrogen bond.
Ice crystals grow as thin hexagonal plates or long hexagonal columns, depending on temperature.
The basal face if typically the surface which shows hexagonal symmetry. For example, the basal face in figure 1 is the surface facing the reader. Both the upper and lower surfaces are basal faces. The prism face is perpendicular to the basal face. It faces outward from an arm or portion of an arm.