Physics Nuclear Physics BUMHS 2024
PMDC Verified Question 14 of 98
Mass number of an atom represents the number of:
A
Proton
B
Neutron
C
Neutron plus proton
D
Proton plus electron
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Neutron plus proton


Concept:

The mass of an atom is overwhelmingly concentrated purely within its nucleus.

Solution:

  • Protons and Neutrons each weigh approximately 1 atomic mass unit (amu).


  • Electrons are nearly 2000 times lighter, contributing almost zero significant mass to the atom.


  • Therefore, the total Mass Number (\(A\)) is calculated by adding together the total count of heavy nucleons: Neutrons plus Protons.


Why other options are incorrect:

Protons alone are the Atomic Number (\(Z\)). Neutrons alone are simply the neutron number (\(N\)). Adding electrons provides a mathematically meaningless value.

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