Lanthanide elements, actinides compared crystal structures

This chapter is intended to provide a unified view of selected aspects of the physical, chemical, and biological properties of the actinide elements. The f block elements have many unique features, and a comparison of the lanthanide and actinide transition series provides valuable insights into the properties of both. Comparative data are presented on the electronic configurations, oxidation states, redox potentials, thermochemical data, crystal structures, and ionic radii of the actinide elements, together with a miscellany of topics related to their environmental and health aspects. Much of this material is assembled in tabular and graphical form to facilitate rapid access. Many of the topics covered in this chapter, and some that are not discussed here, are the subjects of subsequent chapters of this work, and these may be consulted for more comprehensive treatments. This chapter provides a welcome opportunity to discuss the biological and environmental aspects of the actinide elements, subjects that were barely mentioned in the first edition of this work but have assumed great importance in recent times. 

Because the trivalent state exists for all the lanthanides and most of the actinides, variations in chemical properties with ionic radius are often compared for the two series. In general, those changes in crystal structure or other properties that depend on ionic size occur two elements earlier in the 4f series than in the Sf series. This is because the trivalent ion with a particular number of 5f electrons is larger, by about 0.03 A in the transuranic region, than the trivalent ion with an equal number of 4f electrons. 

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