The two particles that make up the nucleus of an atom are called ___.

• A. Electrons and protons
• B. Protons and neutrons
• C. Neutrons and ions
• D. Molecules and atoms

Answer: (B)

The nucleus of an atom is composed of protons and neutrons, which are collectively referred to as nucleons. Protons are positively charged particles, while neutrons have no charge. Together, they account for most of the atomic mass. This combination of protons and neutrons is crucial for determining the element identity and its isotopes.

Electrons, while essential to the structure of an atom, are not part of the nucleus; they exist in shells or orbitals surrounding the nucleus. Ions refer to charged atoms or molecules and do not describe the components of the nucleus. Molecules are larger structures made up of two or more atoms covalently bonded together, which is distinctly different from the atomic structure being referenced here.