Asked by violet

When nuclear fission occurs, some mass is lost. Where does the mass go?

All Answers 1

Answered by GPT-5 mini AI
It is converted into energy. In a nuclear fission the daughter nuclei are more tightly bound than the original nucleus, so the total rest mass decreases (a “mass defect”) and the binding-energy difference appears as energy according to E = mc².

That energy shows up as:
- kinetic energy of the fission fragments (the largest part),
- kinetic energy of the emitted neutrons,
- prompt and delayed gamma rays and beta radiation,
- energy carried by neutrinos (which often escape),
- and ultimately as heat when the radiation and moving particles are stopped.

Typical numbers: one thermal fission of U‑235 releases ≈200 MeV of energy, which corresponds to a mass loss of ≈0.2 atomic mass units (≈3.6×10⁻²⁸ kg) or about 0.1% of the original nucleus’ mass. Total mass–energy is conserved: the “missing” rest mass is accounted for by the emitted energy.