Which statement correctly describes the basic atomic structure?

• A. Protons and neutrons in the nucleus, electrons orbit in shells
• B. Protons orbit the nucleus, electrons reside in the nucleus
• C. Neutrons orbit the nucleus, protons orbit electrons
• D. Electrons orbit the nucleus, protons and neutrons orbit electrons

Answer: (A)

Atoms have a dense nucleus that contains protons and neutrons, with electrons arranged around the nucleus in shells or orbitals. This configuration reflects the basic charge distribution: positively charged protons and neutral neutrons cluster in the center, while negatively charged electrons occupy the surrounding space held by attraction to the nucleus. In the simplest description, electrons “orbit” the nucleus in shells or occupy orbitals around it.

This is why the statement pairing protons and neutrons in the nucleus with electrons orbiting the nucleus is correct. The other ideas mix up locations: the nucleus does not host electrons, and protons or neutrons do not orbit electrons or orbit the nucleus in the way described by the other options.