Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Fission and Fusion
Name: Mark
Status: student
Age: 16
Location: N/A
Country: N/A
Date: 2000-2001


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


Replies:
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



Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory