Fission and Fusion
Two major ways nuclei release energy
Nuclear fission
Fission is the splitting of a heavy nucleus into two smaller nuclei, often after absorbing a neutron. This process can release energy and additional neutrons.
Nuclear fusion
Fusion is the joining of two light nuclei to form a heavier nucleus. It also releases energy when the final nucleus is more tightly bound than the starting nuclei.
Fission vs fusion
Fission
- Splits a heavy nucleus
- Can produce a chain reaction
- Used in nuclear power plants
Fusion
- Combines light nuclei
- Requires very high temperature and pressure
- Powers the Sun and stars
Why energy is released
Energy is released when products have greater binding energy per nucleon than the reactants, so the final state is more stable.
Chain reactions
In fission, emitted neutrons can trigger more fissions. If enough neutrons cause new fissions, the process can sustain a chain reaction.
Which process powers the Sun?
The Sun produces energy mainly by fusing light nuclei into heavier nuclei.
Correct answer: Fusion
Which process splits a heavy nucleus: fission or fusion?
Fission means splitting.
Correct answer: fission
Why can fission produce a chain reaction?
Neutrons released in one fission can cause neighboring nuclei to fission too.
Correct answer: Because emitted neutrons can trigger more fissions