The energy that powers the stars, the destructive force of atomic bombs, the promise of clean and inexhaustible energy: all these are manifestations of nuclear reactions . Since humanity discovered the power hidden in the nucleus of atoms, the field of nuclear physics has undergone a journey of extraordinary discoveries, technical challenges and profound ethical reflections.
Atoms, which have always been considered the fundamental “buildings” of matter, hide in their nucleus a world of particles and forces that operate on infinitesimal scales, but with macroscopic consequences. When atomic nuclei interact with each other, nuclear reactions occur. These can lead to the fusion of light nuclei, as occurs in stars, or to the splitting of heavy nuclei, as occurs in nuclear reactors and atomic bombs.
Unlike chemical reactions, where electrons are the protagonists and nuclei remain unchanged, in nuclear reactions it is the nucleus itself that is transformed . These transformations release or absorb enormous amounts of energy, often millions of times greater than that of chemical reactions. Einstein’s famous formula,AND=��2, tells us that mass and energy are closely linked, and in nuclear reactions we see this equivalence in action: small changes in mass can release enormous amounts of energy.
The mathematics and physics of nuclear reactions are complex, but critical to understanding and controlling these powerful processes. Let’s discover its features together!
Definition of nuclear reaction
A nuclear reaction is the transformation of one or more nuclei (called reactants) into one or more nuclei (called products) different from the starting ones. A nuclear reaction is a process in which two atomic nuclei or a particle and a nucleus interact, resulting in the nucleus itself changing. This can involve the transformation of one element into another, the release or absorption of particles and, often, the release of a large amount of energy. An example of this can be radioactive decay , where an unstable nucleus emits a particle, such as an electron or a positron, transforming into another nucleus.
Definition of nuclear fission
Nuclear fission is a nuclear reaction in which a high-mass nucleus, spontaneously or because it is hit by a neutron, splits into two (or more) lighter nuclei, releasing energy. In this case, a heavy nucleus splits into two or more lighter nuclei, releasing a significant amount of energy. This process underlies the operation of nuclear power plants and atomic bombs . A common example of fission is the splitting of the nucleus of uranium-235 when it absorbs a neutron.
Definition of nuclear fusion
Nuclear fusion is a nuclear reaction in which two light nuclei combine to form a heavier nucleus, releasing energy equivalent to the difference in mass of the reaction. It is the reaction that powers the Sun and other stars. On our planet, controlled fusion is the subject of intense research as a potential source of clean and inexhaustible energy, but achieving the conditions necessary to sustain a fusion reaction is extremely challenging.