The mass number of an atom is the number of
A) protons in the atom.
B) neutrons in the atom.
C) protons plus electrons in the atom.
D) electrons plus neutrons in the atom.
E) neutrons plus protons in the atom.

Question

Quizplus · Accepted Answer

The mass number of an atom is defined as the sum of the number of protons and neutrons in its nucleus, which is option E. Protons and neutrons contribute to the mass of an atom, whereas electrons have negligible mass.

The Mass Number of an Atom Is the Number of