Differences between fission and fusion are:
Fission
1. In a fission reaction, a heavy nucleus breaks up to form two lighter nuclei.
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2. Nuclear fission is a chain reaction,
3. Fission reactions are carried out by bombarding the heavy nuclei with neutrons.
4. Nuclear fission reactions have been controlled to generate electricity.
5. Nuclear fission produces a large amount of energy.
Fusion
1. In a fusion reaction, two light nuclei combine to form a heavy nucleus.
2. Nuclear fusion is not a chain reaction.
3. Fusion reactions are carried out by heating the light atoms to an extremely high temperature.
4. Nuclear fusion reactions have not been controlled so far.
5. The energy produced in a nuclear fusion reaction is much more than that produced during fission.