Where is most of the weight/substance in an atom?

• A. Electron Cloud
• B. Protons and Neutrons in the Nucleus
• C. Nucleus
• D. Electron Shells

Answer: (C)

Mass is concentrated in the nucleus. Protons and neutrons inside the nucleus carry almost all of the atom’s mass, while electrons are much lighter. The electron cloud or shells describe where electrons are, but their mass is negligible by comparison. So, despite the nucleus being tiny in size, it holds nearly all the weight of the atom.