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Question A6 The uranium decay series from U-238 to stable lead (Pb-206) is: 338 U 234Th → 34 Pa + 234 U → 230 Th 238 Ra + 23% Rn → 28 Th +2314 Pb + 233Bi + 34 Po - 90 90 +372 Pb + 2 Bi Po → Pb U-238 has a half-life of 4.5 billion years. Of the other nuclei on the way from U-238 to stable Pb- 206, most are very short-lived (half-lives less than a few months). The exception is radium, with a half-life of 1600 years. Marie Curie was given ten tonnes of pitchblende (uranium ore, mostly uranium oxide) and after several years of chemical processing and purification she isolated some radium from it. Estimate how much radium there was in the pitchblende for her to extract.