fast moving
slow moving
critical neutrons
neutrons at rest
light weight atoms
heavy weight atoms
critical atoms
zero weight atoms
kinetic energy of neutrons
kinetic energy of fission products
instantaneous release of gamma rays
gradual radioactive decay of fission products
alpha particles
beta particles
thermal neutrons
fast neutrons and gamma rays
the original elements change into completely different elements
the electrons of the element change
the molecules rearrange themselves to form other molecules
none of the above.