| 11. | Cranston then published their notes on isotopes, including the new element, Protactinium.
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| 12. | Tetravalent protactinium is chemically similar to uranium ( IV ) and thorium ( IV ).
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| 13. | Heating the nitrate in air at 400 �C converts it to the white protactinium pentoxide.
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| 14. | In hydrides and nitrides, protactinium has a low oxidation state of about + 3.
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| 15. | In 1918 he announced discovery of a stable isotope of Protactinium, working with John Arnold Cranston.
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| 16. | In 1900 William Crookes isolated protactinium as a radioactive material from uranium which he could not identify.
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| 17. | Thus tetravalent protactinium in solutions is obtained by the action of strong reducing agents in a hydrogen atmosphere.
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| 18. | Protactinium was first identified in 1913 by Kasimir Fajans and Oswald Helmuth G�hring at the University of Karlsruhe.
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| 19. | Protactinium is more abundant ( 10 " 12 % ) in the Earth's crust than actinium.
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| 20. | Heating PaP 2 O 7 in air to 1400 �C decomposes it into the pentoxides of phosphorus and protactinium.
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