We present in this work a discussion on the quantitative bonding information that can be deduced from the topological analysis of the crystal wave function of 120 alkali halide perovskites. The formalism, recently presented, is a development of the theory of atoms in molecules of Bader into the domain of crystalline materials. We discuss the shape of the ions and show how the classical picture in terms of slightly deformed spheres is contained in the topological description. The nature of the chemical bond in these systems is depicted by means of graphical representation of the electron density and its Laplacian along the surfaces of the attraction basins. The ionicity of the crystals and the behaviour of the ionic radii are also briefly reviewed.