The red arrow in the graph (see margin) indicates the changes that occur in the nucleus of an atom during a nuclear reaction. Identify the isotopes involved as product and reactant, and name the type of decay process.

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. This difference in neutron count results in varying atomic masses. For example, carbon-12 and carbon-14 are isotopes of carbon, with 6 protons and 6 or 8 neutrons, respectively. Understanding isotopes is crucial in nuclear reactions, as they can change during decay processes.

Nuclear decay is the process by which an unstable atomic nucleus loses energy by emitting radiation. This can occur in various forms, including alpha decay, beta decay, and gamma decay. In beta decay, a neutron is transformed into a proton, resulting in an increase in atomic number while the mass number remains unchanged. Recognizing the type of decay helps in identifying the isotopes involved in the reaction.

The atomic number of an element is defined by the number of protons in its nucleus, which determines the element's identity. The number of neutrons, on the other hand, contributes to the mass of the atom and can vary among isotopes. In the context of the provided graph, the changes indicated by the red arrow reflect a transition in the atomic number and neutron count, illustrating the transformation of one isotope into another during a nuclear reaction.