Final answer:
The mass defect of a deuterium nucleus is the difference between the combined mass of its components and its actual mass, which is 0.002388 amu. This defect represents the nuclear binding energy and correlates with nucleus stability.
Step-by-step explanation:
The mass defect in atomic mass units (amu) for a deuterium nucleus is calculated by taking the difference between the mass of the individual components (a proton and a neutron) and the actual mass of the deuterium nucleus. The mass of a neutron and a proton together is approximately 2.016490 amu, while the experimentally measured mass of a deuterium nucleus is approximately 2.014102 amu. Therefore, the mass defect is 2.016490 amu - 2.014102 amu, which equals 0.002388 amu. This difference corresponds to the nuclear binding energy, which relates to the stability and energy content of the nucleus.
The larger the value of the mass defect, the greater the nuclear binding energy and the more stable the nucleus. Equation 21.8.4 relates the loss in mass to energy release when a nucleus forms from isolated protons and neutrons, illustrating that nuclear reactions involve significantly greater energy changes compared to chemical reactions.