Why is the measured mass of an atomic nucleus always less than the sum of the rest…
PHYSICS · Single correct · A Level · Physics · Nuclear physics · Nuclear physics
Problem
Why is the measured mass of an atomic nucleus always less than the sum of the rest masses of its constituent protons and neutrons?
(a) The mass discrepancy is a relativistic effect that makes free neutrons slightly heavier than bound neutrons, so the sum appears larger.
(b) Binding of nucleons lowers their kinetic energy, and this reduced kinetic energy shows up as a negative mass according to E=mc2. Hence the measured mass is smaller.
(c) A part of the mass is converted into energy that is released when the nucleus is formed.
(d) Protons lose mass because their positive charge is neutralised inside the nucleus, so the total nuclear mass is less.