A radioactive actinide metal, neptunium is the first transuranic element. Neptunium is a hard, silvery, ductile, radioactive actinide metal. Thorium is a moderately soft, paramagnetic, bright silvery radioactive actinide metal. Lead is created in the Earth via decay of actinide elements, primarily uranium and thorium. In general, most actinide isotopes with an odd neutron number are fissile. As a member of the actinide series, it is the seventh transuranic element. The atomic nuclei of the actinide elements are shaped like prolate spheroids. It is the third-to-last actinide and the ninth transuranic element. A number of actinide compounds are ferromagnets at room temperature or exhibit ferromagnetism upon cooling. Lanthanide and actinide aqua ions have a solvation number of 8 or 9. RT can be used to synthesize actinide complexes. The hydrated salts are also used for the extraction of actinide elements. An is used in general discussions of actinide chemistry to refer to any actinide. It is a silvery-grey metal in the actinide series of the periodic table.