What term refers to the sum of protons and neutrons in an atom, representing its mass?

• A. Atomic Number
• B. An Atom
• C. Atomic Mass
• D. Ion

Answer: (C)

Mass of an atom comes mainly from its protons and neutrons; electrons contribute very little to the total mass. The term that describes the atom’s mass as a whole is atomic mass, typically measured in atomic mass units. This mass is essentially set by the number of nucleons, so it closely mirrors the sum of protons and neutrons (the exact sum is the mass number). Among the options, atomic mass best communicates the idea of the atom’s overall mass. Atomic number refers to the count of protons, the identity of the element; an ion is a charged atom, and simply saying an atom doesn’t specify its mass.