them, is usually highly toxic. Radium has a low availability and is highly radioactive, making it toxic to life. Extensions The next alkaline earth metal after radium is thought to be element 120, although this may not be true due to relativistic effects. The synthesis of element 120 was first attempted in March 2007, when a team at the Flerov Laboratory of Nuclear Reactions in Dubna bombarded plutonium-244 with iron-58 ions; however, no atoms were produced, leading to a limit of 400 fb for the cross-section at the energy studied. In April 2007, a team at the GSI attempted to create element 120 by bombarding uranium-238 with nickel-64, although no atoms were detected, leading to a limit of 1.6 pb for the reaction. Synthesis was again attempted at higher sensitivities, although no atoms were detected. Other reactions have been tried, although all have been met with failure. The chemistry of element 120 is predicted to be closer to that of calcium or strontium instead of barium or radium. This noticeably contrasts with periodic trends, which would predict element 120 to be more reactive than barium and radium. This lowered reactivity is due to the expected energies of element 120's valence electrons, increasing element 120's ionization energy and decreasing the metallic and ionic radii. The next alkaline earth metal after element 120 has not been definitely predicted. Although a simple extrapolation using the Aufbau principle would suggest that element 170 is a congener of 120, relativistic effects may render such an extrapolation invalid. The next element with properties similar to the alkaline earth metals has been predicted to be element 166, though due to overlapping orbitals and lower energy gap below the 9s subshell, element 166 may instead be placed in group 12, below copernicium. See also Alkaline earth octacarbonyl complexes Explanatory notes References Bibliography Further reading Group 2 – Alkaline Earth Metals, Royal Chemistry Society. Hogan, C. Michael. 2010. "Calcium". A. Jorgensen, C. Cleveland, eds. Encyclopedia of Earth. National Council for Science and the Environment. Maguire, Michael E. "Alkaline Earth Metals". Chemistry: Foundations and Applications. Ed. J. J. Lagowski. Vol. 1. New York: Macmillan Reference USA, 2004. 33–34. 4 vols. Gale Virtual Reference Library. Thomson Gale. Petrucci R.H., Harwood W.S., and Herring F.G., General Chemistry (8th edition, Prentice-Hall, 2002) Silberberg, M.S., Chemistry: The Molecular Nature of Matter and Change (3rd edition, McGraw-Hill, 2009) Groups (periodic table) Periodic table