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Name: Mark
Status: student
Age: 16
Location: N/A
Country: N/A
Date: 2000-2001

Can any atom undergo fission or fusion?? how is it that both fission and fusion release energy??

Here's an approximate rule of thumb: Fusion releases energy when the product is lower than around iron in the periodic chart. Fission releases energy when the precursor is higher than around iron. The root cause of this is that the electrostatic force is long range while the nuclear force is short range, so repulsion between protons becomes increasingly important as the nucleus gets larger.

This is why stars blow up, by the way. They fuse stuff until they make iron, and then they get upset when it no longer works.

Tim Mooney

Yes, any atom may undergo fission or fusion, but either or both processes may require energy. It's all a matter of energetics: if the initial atom is lower in energy that the final products, the process will require energy. If the initial atom is higher in energy than the final products, the process will release energy.

Generally, it is fission of the heavy elements and fusion of the light elements that release energy. This is because the most stable nuclei have intermediate weights: iron is about as good as it gets. Other very stable nuclei include carbon-12 and helium-4. Other considerations for other types of radioactive decay include the proton/neutron ratio of the nucleus and the internal energy state of the nucleus.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois

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