Reduction in mass per nucleon after fission, greatest to least: Uranium, Silver, Gold, Iron.
Work Step by Step
Look at Figure 34.16. Uranium is far to the right, and has a lot of mass per nucleon. After a fission process, each of the pieces will have less mass per nucleon (they pieces are still heavier than iron). Iron already has the least mass per nucleon, so if it is forced to undergo fission by nuetron bombardment, it will have no reduction in mass per nucleon. There is not enough information in the text or in Figure 34.16 to choose between silver and gold. This is discussed on pages 647-648.