Which parts of an atom contribute most to its mass?

• A. Protons and neutrons
• B. Electrons only
• C. Neutrons and electrons
• D. Protons only

Answer: (A)

Verified step by step guidance

1. Recall the basic structure of an atom, which consists of protons, neutrons, and electrons.
2. Understand that protons and neutrons are located in the nucleus, while electrons orbit around the nucleus.
3. Know that the mass of protons and neutrons is approximately 1 atomic mass unit (amu) each, whereas electrons have a much smaller mass (about 1/1836 of a proton).
4. Since electrons have negligible mass compared to protons and neutrons, the majority of an atom's mass comes from the nucleus.
5. Therefore, the parts of an atom that contribute most to its mass are the protons and neutrons.