Final answer:
In a nuclear reaction, the correct statement is that the identity of the element changes because the nucleus of the atom is altered, leading to a change in the atomic number.
Step-by-step explanation:
The question asks which statement is true for a nuclear reaction. In a nuclear reaction, the identity of an element can change because these reactions involve changes in the nucleus, such as altering the number of protons or neutrons. Therefore, option (c) the identity of the element changes, is correct. Unlike in chemical reactions, where electrons are transferred or shared but the nucleus remains unchanged, nuclear reactions can transmute one element into another and often release large amounts of energy. During this process, an atom may capture or release neutrons, protons, alpha particles (helium nuclei), beta particles (high-energy electrons or positrons), or gamma rays, resulting in a change of the atomic number and, consequently, the identity of the element.