What is positron emission? What is the symbol for a positron?

Radioactive decay is a natural process by which an unstable atomic nucleus loses energy by emitting radiation. This spontaneous transformation leads to the creation of different elements or isotopes. Positron emission, as covered in the step by step solution, is specifically one type of radioactive decay. It generally occurs in proton-rich isotopes, which means these nuclei have more protons than stable nuclei typically have.
During positron emission, one of the protons in the nucleus is converted into a neutron. This is accompanied by the release of a positron—the antimatter counterpart of the electron—and an electron neutrino, which is nearly massless and carries away some energy. The process reduces the nucleus's charge without changing its mass, thus altering the atomic number of the element while the mass number remains constant. For students to fully appreciate the intricacies of radioactive decay, understanding the various types including alpha, beta (beta-minus and beta-plus or positron emission), and gamma decay is crucial.

Subatomic particles are the building blocks of atoms, too small to be visible even with the most powerful microscopes. Understanding these particles is essential when studying processes like positron emission. There are primarily three types of subatomic particles: protons, neutrons, and electrons.
Protons carry a positive electrical charge and reside within the atomic nucleus. Neutrons, on the other hand, have no charge and are also located in the nucleus. Electrons, which are negatively charged, orbit the nucleus. Each of these particles has a corresponding antiparticle with the same mass but opposite charge. For instance, the positron, symbolized as \( e^+ \) or \( \beta^+ \), is the antiparticle of the electron. This fundamental knowledge helps students to not only grasp the concepts behind radioactive decay but also the broader topic of particle physics.

Proton-rich isotopes are variants of elements with an unusual number of protons in their nuclei, often leading to instability. These isotopes are prone to undergoing radioactive decay to reach a more stable configuration.
In the context of positron emission, a proton-rich nuclide loses a proton by transforming it into a neutron. This is an effort to achieve a more favorable proton-to-neutron ratio, characteristic of stable isotopes. Since the number of protons determines the chemical identity of an element, this transformation results in the formation of a different element with a lower atomic number. However, the mass number, which is the sum of protons and neutrons, remains unchanged because the total number of nucleons (protons and neutrons together) does not alter during positron emission. The understanding of why and how proton-rich isotopes undergo this specific decay provides insight into the forces and interactions within an atomic nucleus.

A neutrino is an extremely elusive subatomic particle that is electrically neutral and has an almost negligible mass. It is often produced in nuclear reactions, such as those occurring in the sun, during nuclear fusion, and, importantly, in certain types of radioactive decay including positron emission.
In positron emission, alongside the positron, an electron neutrino \( u_e \) is emitted. Neutrinos interact very weakly with matter; billions of them pass through us every second without any effect. Despite their elusive nature, neutrinos are fundamental to our understanding of particle physics and the universe. They come in three types or 'flavors' associated with electrons, muons, and tau particles. Research into neutrinos and their properties is ongoing, as they hold the potential to answer key questions about the fundamental workings of the universe.