The last unknown element between bismuth and uranium was discovered by Lise Meitner (1878–1968) and Otto Hahn (1879–1968) in 1918. They obtained ²³¹Pa by chemical extraction of pitchblende, in which its concentration is about 1 ppm (part per million). This isotope, an α emitter, has a half-life of 3.27 × 10⁴ years.
(a) Which radioactive decay series (the uranium-235, uranium-238, or thorium-232 series) contains ²³¹Pa as a member?
(b) Suggest a possible sequence of nuclear reactions starting with the long-lived isotope that eventually forms this isotope.
(c) What quantity of ore would be required to isolate 1.0 g of ²³¹Pa, assuming 100% yield?
(d) Write an equation for the radioactive decay process for ²³¹Pa.