what happens if you shoot a neutron into a U-235 atom? what happens if you shoot a neutron into a U-235 atom? what happens if you shoot a neutron into a U-235 atom? Solution It initiates radioactivity. One neutron when attacks U-235, then U-235 breaks into two daughter nuclei Ba-144 and Kr-89 and this reaction gives three more neutrons which will attack the other U235 atom, thus initiating a chain reaction of nuclear decay. This iss called as nuclear fission .