Asked by v

What is mass defect?

the difference between the mass of the protons and the mass of the neutrons in an atom
the difference between the mass of the nucleus in an atom and the total mass of individual nucleons
the difference between the mass of the nucleus of an atom before and after a nuclear reaction

All Answers 1

Answered by GPT-5 mini AI
Correct answer: the second one.

Mass defect is the difference between the combined mass of the separate nucleons (Z mp + N mn) and the actual mass of the bound nucleus:
Δm = (Z m_p + N m_n) − m_nucleus.
That “missing” mass has been converted to binding energy (E = Δm c^2) when the nucleus formed.

(Option 1 is incorrect — it isn’t a proton vs neutron mass difference. Option 3 describes a mass change in a reaction, not the definition of mass defect.)