Final answer:
A proton is a positively charged subatomic particle found in the nucleus of an atom, essential in defining the atomic number and hence the identity of the element. The number of protons contributes to an element's properties, including the possibility of being a radioactive isotope involved in nuclear decay.
Step-by-step explanation:
A proton is a subatomic particle found in the nucleus of an atom. It is one of the components that make up the atom, alongside neutrons. Protons are characterized by a positive electrical charge, which is equal in magnitude and opposite in sign to the negative charge carried by an electron. The presence of protons in the nucleus contributes to the majority of an atom's mass. In addition to charge and mass, a proton's identity helps define the chemical element: each element is distinguished by the number of protons in its atomic nuclei. For example, hydrogen has one proton, while carbon has six protons.
One important aspect of protons is their role in quantum mechanical tunneling, a phenomenon where particles can pass through potential energy barriers despite not having enough energy. This effect is crucial in the process of radioactive decay, wherein an unstable nucleus can emit particles to become more stable—a process observed with a radiation detector. As a matter of fact, the number of protons in the nucleus also defines whether an isotope is radioactive. A radioactive isotope is one that spontaneously emits particles or energy to form a more stable element.