Question

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?
1 only
2 only
1 and 2 only
1, 2, and 3

Answer 1

Answer: "1 and 2 only."

Explanation: 1 and 2 are both correct. The mass defect is the small amount of mass lost when nucleons bind (statement 1), and the nuclear binding energy is the energy equivalent of that mass defect — i.e., the energy you must supply to separate the nucleons (statement 2). Statement 3 is wrong because it swaps the two definitions.