A student writes the following statements about the relationship between mass defect and nuclear binding energy.1. When an isotope’s protons and neutrons come together to form a nuclide, a small amount of mass is converted to energy.2. An equivalent amount of energy must be added to the nuclide to split apart its protons and neutrons.3. Statement 1 describes the isotope’s nuclear binding energy, and statement 2 describes the isotope’s mass defect.Which statement is correct?

When protons and neutrons bind to form a nuclide, the mass of the nuclide is less than the combined mass of its separate particles; the difference is converted into energy. That energy is the nuclear binding energy, and an equal amount must be supplied to separate the nuclide into its protons and neutrons. The mass defect is the missing mass, not the energy, so statement 3 is incorrect. Therefore, the correct choice is C, 1 and 2 only.

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