Actinide elements 166 xenon

It is no surprise that the majority of the noble gases, krypton and xenon, have been lost, nor that there are still traces trapped in some of the core minerals. The relatively soluble alkali and alkaline earth elements have also been lost to a large extent, as have molybdenum, cadmium and iodine. The elements zirconium, technetium, lead, and to some extent ruthenium have at least been redistributed in the core. The rare earth elements, cerium, neodymium, samarium, and gadolinium as well as the actinides, thorium, uranium, neptunium, and plutonium show little evidence of migration, except possibly near the periphery of the core. By analogy to the rare earth elements it is probable that the transplutonium actinides, americium, curium, etc. would not migrate in this same environment. 

Periodic table of the elements. The lanthanide series ( rare earths ), beginning with lanthanum (57), and the actinide series, which begins with actinium (89) and includes thorium (90) and uranium (92), are chemically similar. Other families of elements read vertically down the table—at the far right, for example, the noble gases helium, neon, argon, krypton, xenon, radon. 

Suggested electron configurations (beyond radon and xenon) for gaseous atoms of actinide and lanthanide elements. 

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