Which reaction releases energy during the combination of atomic nuclei?

The reaction that releases energy during the combination of atomic nuclei is nuclear fusion. This process occurs when two light atomic nuclei combine to form a heavier nucleus, resulting in the release of a significant amount of energy. This is the same process that powers the sun and other stars, where hydrogen nuclei fuse to form helium and release energy in the form of light and heat.

In nuclear fusion, the energy produced comes from the strong nuclear force that binds protons and neutrons in the nucleus, which results in a mass defect. The mass of the resulting nucleus is less than the sum of the masses of the original nuclei, and this missing mass is converted into energy according to Einstein’s mass-energy equivalence principle, E=mc².

The other processes mentioned, such as nuclear fission, chemical bonding, and radioactive decay, involve different mechanisms and energy considerations. Fission involves splitting heavy atomic nuclei and releases energy but does so through a different pathway than fusion. Chemical bonding deals with the rearrangement of electrons rather than atomic nuclei, and radioactive decay involves the transformation of unstable isotopes, often leading to the release of particles and energy but not through nuclear fusion.