How can a nucleus be described by particular values of A, Z and N when the mass of the nucleus is not equal to Zmp + Nmn, where mp and mn are the masses of free protons and neutrons?
A)A, Z and N have no intrinsic meaning.
B)A, Z and N describe the number of particles of given types, but mass has no meaning when part of the mass is elsewhere in the universe.
C)A, Z and N describe the number of particles an ideal rather than a real nucleus would have.
D)A, Z and N describe the number of particles of given types in the nucleus, but not their masses in a bound state.
E)A, Z and N describe the number of particles of given types in the nucleus since the missing mass consists of electrons that are also present in the nucleus.

Question

Quizplus · Accepted Answer

A, Z and N describe the number of particles of given types in the nucleus, but not their masses in a bound state. This is because the mass of a bound nucleus is slightly less than the sum of the masses of its constituents due to the release of binding energy during formation. Therefore, A, Z and N are still meaningful descriptors of the nucleus, but the mass cannot be determined simply by adding the masses of its constituent particles.

How Can a Nucleus Be Described by Particular Values of A