Explain the difference between nuclear fission and nuclear fusion. In your answer, refer to the nuclei involved in each process.

Nuclear fission is the splitting of a large, unstable nucleus (e.g. Δ‑Uranium) into two smaller, more stable nuclei, releasing neutrons and gamma rays.
Nuclear fusion is the joining of two small, light nuclei (e.g. two Δ‑deuterium nuclei) to form a larger, heavier nucleus, also releasing energy.
Both processes release energy because the mass of the products is less than the mass of the reactants.
Fission produces two smaller nuclei plus neutrons, whereas fusion produces a single heavier nucleus and very few neutrons.