For elements lighter than iron, what happens to the nuclear binding energy per nucleon when two nuclei fuse together?

1. For nuclei lighter than iron, the nuclear strong force is proportionally stronger relative to the Coulomb repulsion than in heavier nuclei. 2. When such a light nucleus absorbs more nucleons, it becomes more tightly bound, and energy is released as a result. 3. This means the binding energy per nucleon increases when light nuclei fuse, releasing energy rather than requiring it. 4. Binding energy per nucleon does not stay the same across all light elements, and it certainly does not turn negative. 5. So increasing binding energy per nucleon, releasing energy, is correct. _Source: OpenStax Physics (CC BY 4.0), Ch 22 "The Atom", section 22.4 Nuclear Fission and Fusion_