Crystal structures of three new uranyl compounds were solved using single crystal X-ray diffraction and studied using FTIR spectroscopy. Although the syntheses conditions were very similar differing only in the alkaline earth metal (Mg, Ca or Sr), the resulting structures are different, containing, respectively, mono-, tri- and hexanuclear metal-containing building units. This fact proves the profound crystal-chemical role of secondary metal atoms on the formation of crystal structures. Parameters of alkaline earth metal cations in the three newly synthesized compounds as well as in the earlier reported Ba-containing analog are discussed in detail using Voronoi–Dirichlet polyhedra and the method of intersecting spheres. Differences in packing of building units in the four mentioned compounds, as well as inter- and intramolecular noncovalent interactions in their structures are reported. The results of analysis are consistent with the stereoatomic model of crystal structures.