Mass Defect: Which statement is correct?

Mass Defect: Which statement is correct?

• A. A nucleus weighs more than the sum of its constituent nucleons
• B. A nucleus weighs a little less than its constituent nucleons
• C. Mass defect is zero
• D. Mass defect equals the sum of the binding energy

Answer: (B)

When nucleons bind to form a nucleus, energy is released, and the total mass of the bound system is slightly less than the sum of the masses of the individual nucleons. That shortfall is the mass defect. Because energy is released during binding, the nucleus ends up weighing a little less than its constituent nucleons, which is exactly what the statement describes. The amount of energy associated with this mass difference is the binding energy, related by E = Δm c^2, so the mass defect and the binding energy are different expressions of the same phenomenon.

When nucleons bind to form a nucleus, energy is released, and the total mass of the bound system is slightly less than the sum of the masses of the individual nucleons. That shortfall is the mass defect. Because energy is released during binding, the nucleus ends up weighing a little less than its constituent nucleons, which is exactly what the statement describes. The amount of energy associated with this mass difference is the binding energy, related by E = Δm c^2, so the mass defect and the binding energy are different expressions of the same phenomenon.