The atomic mass is equal to the sum of the
A) neutrons and isotopes.
B) neutrons and electrons.
C) neutrons and protons.
D) protons, neutrons, and electrons.
E) protons only.

Question

Quizplus · Accepted Answer

The atomic mass number is the sum of the number of protons and neutrons in the atomic nucleus. Electrons are not included in the calculation of atomic mass because their mass is insignificant compared to protons and neutrons. Isotopes are variants of an element with different numbers of neutrons, but again, the atomic mass is based on the sum of protons and neutrons, so option A is incorrect. Option B is incorrect as well, as the number of electrons does not contribute to the atomic mass. Option D is partially correct in that it includes protons and neutrons, but it is unnecessarily inclusive as it also includes electrons, which we know do not contribute to atomic mass. Option E is incorrect as it only includes the number of protons, whereas we know that both protons and neutrons are important in calculating atomic mass.

The Atomic Mass Is Equal to the Sum of the