Fission Reactions In a nuclear fission reaction a heavy nucleus divides to form smaller nuclei and one or more neutrons. Many nuclei can undergo fission, but the fission reactions of uranium-235 and plutonium-239 are the principal ones that generate energy in nuclear power plants. This problem deals with balancing the fission reaction of the uranium-235 isotope as it undergoes bombardment from a neutron.

Part A When a^235 U_92 nucleus is bombarded by neutrons (^1 n _0) it undergoes a fission reaction, resulting in the formation of two new nuclei and neutrons. The following equation is an example of one such fission process:^235 U_92 +^1 n _0 rightarrow^A Ba _Z +^94 Kr _36 + 3^1 n _0 Enter the isotope symbol for the barium (Ba) nucleus in this reaction. Express your answer as an isotope.
Part B In another process in which^235_ U 92 undergoes neutron bombardment, the following reaction occurs:^235 U _92 +^1 n _0 rightarrow^A Sr _Z +^143 Xe _54 + 3^1 n _0 Enter the isotope symbol for the strontium (Sr) nucleus in this reaction. Express your answer as an isotope.