The nucleus of an atom contains?

• A. Neutrons and protons
• B. Electrons and protons
• C. Protons only
• D. Electrons only

Answer: (A)

Nucleus houses protons and neutrons—the particles that give the atom its mass and, in the case of protons, define its identity by number of protons. Neutrons add mass and help stabilize the nucleus through the strong force. Electrons, carrying negative charge, reside outside the nucleus in electron clouds or orbitals, attracted to the positively charged protons. So the correct option, stating neutrons and protons, matches what actually lives in the nucleus. The other statements would place electrons inside the nucleus or omit one of the nucleons, which isn’t accurate.