The Mass Number of an Atom is the Total Number

Question

The mass number of an atom is the total number of _______ in its nucleus.
A) electrons
B) protons
C) protons and electrons
D) protons and neutrons
E) charges

Accepted Answer

Mass number is the sum of protons and neutrons in the nucleus. Electrons are not included because they have negligible mass compared to protons and neutrons. Charges are also not included as they can be positive or negative depending on the number of protons and electrons.