Question

1. most of the mass of an atom is concentrated in the:

electron shells
nucleus
protons only
empty space
clear all

Explanation:

To determine where most of an atom's mass is concentrated, we recall atomic structure: electrons have negligible mass, the nucleus contains protons (massive) and neutrons (massive), while electron shells and empty space have little mass. So the nucleus holds most of the atom's mass.

Answer:

B. Nucleus (assuming the options are labeled with "Nucleus" as the correct choice; in the given image, the selected option is "Nucleus", so the answer is the option with "Nucleus", e.g., if options are A. Electron shells, B. Nucleus, C. Protons only, D. Empty space, then B. Nucleus)