Account for rest mass and released energy

Choose a complete system before subtracting

For a specified process, define Δm as the total initial rest mass minus the total final rest mass. Q=Δmc² is positive for a decrease in rest mass. Energy has not vanished: outgoing particles can carry kinetic energy and radiation can carry energy away. A complete isolated system retains the same total energy, including these contributions.

The slider supplies original hypothetical complete mass differences in units of 0.001 u. It does not combine measured nuclide masses or identify a real reaction. Using 1 u c²≈931.494 MeV, a difference 0.010 u gives Q≈9.31494 MeV per event. Convert to joules using 1 MeV=10⁶×1.602176634×10⁻¹⁹ J, giving approximately 1.4924×10⁻¹² J.

Scale the count without changing the event

Five identical events have five times the total released energy but the same Q per event. This is a count multiplier, not a simulated reaction history. It says nothing about how quickly the events occur or whether one event causes another. Energy and power are distinct, just as in the photon lesson.

If the initial-minus-final mass difference were negative, Q would be negative: energy must be supplied for the specified products, and momentum conservation may impose an additional threshold in a laboratory arrangement. The current positive slider intentionally does not model collision thresholds or reaction kinetics.

Keep mass conventions consistent

Nuclear masses exclude orbital electrons; neutral atomic masses include them. Mixing those conventions without accounting for electron numbers can produce a false mass difference, particularly in beta processes. The supplied complete difference avoids that complication for the arithmetic exercise, but a real calculation must state which masses and particle species were used.

Binding is not a stored bag of fuel

Binding energy is the energy needed to separate a bound system into specified constituents, or the corresponding difference in rest energies. A positive binding energy does not imply that arbitrarily breaking apart any nucleus releases energy. The relative initial and final bindings, with full particle accounting, decide the sign of Q. This is conceptual bookkeeping, not a design for a nuclear device.

Source and authorship

Reference for the physical relationship. Source checked 30 October 2026. The explanations, numerical cases, questions and diagrams here are original; reference material is not copied. Exact h,c,e follow NIST SI definitions.