Nuclear chain reaction
A possible nuclear fission chain reaction. In the first step, a uranium-235 atom absorbs a neutron, and splits into two new atoms (fission fragments), releasing three new neutrons and a large amount of binding energy. In the second step, one of those neutrons is absorbed by an atom of uranium-238, and does not continue the reaction. Another neutron leaves the system without being absorbed. However, one neutron does collide with an atom of uranium-235, which then splits and releases two neutrons and more binding energy. In the third step, both of those neutrons collide with uranium-235 atoms, each of which splits and releases a few neutrons, which can then continue the reaction.
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