BU Dental Radiology Practice Exam 2026 – Complete Study Resource

The nucleus is the dense, central region of an atom where the protons and neutrons (the nucleons) reside. Protons carry a positive charge, neutrons are electrically neutral, and electrons form a surrounding cloud held in orbit by the attraction to the positively charged nucleus. Because protons and neutrons are heavy, most of the atom’s mass is concentrated in the nucleus, while electrons contribute very little mass and occupy spaces around the nucleus.

The statement that best fits this arrangement is that protons and neutrons are located in the nucleus. The idea that electrons are inside the nucleus is incorrect because electrons exist outside in electron shells or orbitals. The notion that neutrons have a negative charge is also incorrect since neutrons are neutral.