| 11. | Elements heavier than lead, and the elements technetium and promethium, exist only as radionuclides.
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| 12. | Now only promethium and fermium don't have images; any help is obviously appreciated!
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| 13. | Promethium belongs to the cerium group of lanthanides and is chemically very similar to the neighboring elements.
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| 14. | Marinsky and Glendenin produced promethium both by extraction from fission products and by bombarding neodymium with neutrons.
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| 15. | Following Shocker leads him to Alistair Smythe and the Promethium X, which Spider-Man steals.
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| 16. | Finally, promethium can be formed in nature as a product of spontaneous fission of uranium-238.
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| 17. | It is constructed of promethium and uses highly advanced Martian, Thanagarian, Kryptonian, and Earth technologies.
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| 18. | It was the first to create the element promethium, used in nuclear-powered batteries in guided missiles.
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| 19. | Quite a few years later, this element 61 was created artificially in nuclear reactors and was named promethium.
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| 20. | Many properties of promethium rely on its position among lanthanides and are intermediate between those of neodymium and samarium.
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