An Atom's Atomic Mass is Best Described as the Mass

Question

An atom's atomic mass is best described as the mass of
A)the protons it contains.
B)the neutrons it contains.
C)electrons in the outermost shell.
D)protons and neutrons it contains.
E)protons and electrons it contains.

Accepted Answer

The atomic mass of an atom is primarily determined by the sum of the masses of its protons and neutrons, as electrons have negligible mass.