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