Question

Whether the total mass of nuclei increases, decreases or remains unchanged?

Hint:

In nuclear fusion, the total mass of the nuclei decreases, and the missing mass is converted into energy.

Answer 1

In nuclear reactions like fission and fusion, the total mass of the nuclei can change, increasing, decreasing, or staying the same based on the reaction type. Let's examine each:

1. Mass in Nuclear Fusion:

Nuclear fusion involves combining two light atomic nuclei (e.g., hydrogen) into a heavier one (e.g., helium). Key points:

• The resulting heavier nucleus has a mass slightly less than the combined mass of the initial nuclei.
• This mass deficit is converted into energy, as described by Einstein's \( E = mc^2 \), and released as heat and radiation.
• Consequently, in fusion, the total mass of the products is less than the total mass of the reactants, with the difference being energy release.

2. Mass in Nuclear Fission:

Nuclear fission occurs when a heavy nucleus (e.g., uranium-235 or plutonium-239) splits into two smaller nuclei, also releasing energy. Here's how mass is affected:

• Similar to fusion, the products (smaller nuclei and released neutrons) have a total mass slightly less than the original nucleus.
• This mass difference is converted into energy and released, following \( E = mc^2 \).
• Thus, in fission, the total mass of the nuclei decreases, and the lost mass is emitted as energy.

3. Mass in Nuclear Decay:

During radioactive decay (alpha, beta, or gamma), the parent nucleus's mass is invariably slightly greater than the combined mass of the daughter nucleus and any emitted particles (alpha, beta, etc.). This mass difference is converted into energy, often in the form of radiation.

4. Conclusion:

Both nuclear fusion and fission result in a decrease in the total mass of the nuclei involved, with the deficit converted into energy. However, some nuclear processes, such as stable reactions, might exhibit no mass change. In general, for energy-releasing nuclear reactions (fission, fusion), the total mass declines, manifesting as energy. Therefore, nuclear reactions typically involve a reduction in the total mass of nuclei.