Which part of an atom accounts for most of its mass?

• A. Nucleus
• B. Neutrons only
• C. Protons only
• D. Electron cloud

Answer: (A)

Verified step by step guidance

1. Recall that an atom consists of three main subatomic particles: protons, neutrons, and electrons.
2. Understand that protons and neutrons are located in the nucleus at the center of the atom, while electrons are found in the electron cloud surrounding the nucleus.
3. Recognize that protons and neutrons have approximately the same mass, which is much greater than the mass of electrons.
4. Since the nucleus contains both protons and neutrons, and these particles have most of the atom's mass, the nucleus accounts for nearly all of the atom's mass.
5. Therefore, the electron cloud contributes very little to the total mass of the atom compared to the nucleus.