Nuclear Fission Name Per phet. colorado.edu (Nuclear Fission Simulation) or google PhET > Physics > Quantum Phenomena Background: In this simulation, you will be using two isotopes of uranium. Complete the following information about uranium-235 and uranium-238. 1 . Isotope # protons # neutrons atomic mass uranium-235 uranium-238 Define fusion: Define fission: Using the "Fission: One Nucleus" Tab. . . 2. Run the simulation. Before the gun is fired, is the material stable, or does it seem likely to radioactively decay? 3. When you operate the gun, what type of particle is fired? 4. Describe how you can trigger a fission reaction in the uranium-235 atom. 5. How many neutrons are released when the atom undergoes fission? Using the Chain Reaction Tab. .. 6. What happens when you shoot a neutron at a uranium-238 atom? (Change to U-238 on the right side) 7. What happens when you shoot a neutron at a uranium-239 atom? 8. What happens when you have one hundred U-235 (no U-238) atoms and shoot one neutron