There are many patterns that help us in science. When doing nuclear equations, you know that it is nuclear, not because it has the same types of elements, but because the mass numbers and atomic numbers are equal on both sides. Whereas in a chemical equation, there are the same amounts and same types of each element on each side of the equation. Also, in the chain reaction above, Uranium-235 goes through nuclear fission and produces Barium-142 and Krypton-91 along with 3 neutrons.As the neutrons travel out, they hit other Uranium atoms, causing them to react, and the process to continue. The neutrons of the new reaction than go on to continue the process and the patten keeps on going. (each of the 3 neutrons produced travels out another Uranium atom, causing them to react.) So nuclear chain reactions show patterns is the ways the energy is released.
