The interaction that binds protons and neutrons, protons and protons, and neutrons and neutrons together in the nucleus is known as

• A. Electromagnetic forces
• B. Nuclear forces
• C. Gravitational force
• D. Weak forces

Answer: (B)

The binding in the nucleus comes from the strong nuclear force. This force acts between nucleons—protons and neutrons—over very short distances and is attractive, enough to overcome the electrostatic repulsion between protons. It is effectively the same strength between proton–proton, neutron–neutron, and proton–neutron pairs, which is why all nucleons can be held together in the nucleus.

The electromagnetic force exists between charged protons, and it would push them apart if the strong force weren’t holding them together, so it doesn’t bind the nucleus by itself. Gravitational force is utterly negligible at the atomic scale, and the weak force doesn’t bind nuclei either—it governs certain decay processes, not the binding itself.

So the correct binding mechanism is the nuclear (strong) force.