What does the nucleus of an atom primarily contain?

The nucleus of an atom is primarily composed of neutrons and protons. Protons carry a positive charge, while neutrons are neutral, meaning they do not have any charge. Together, they make up nearly all of the atom's mass and are tightly bound within the nucleus due to the strong nuclear force.

Electrons, on the other hand, are located in the electron cloud surrounding the nucleus, not within it. Their presence is crucial for the chemical properties of the atom, but they do not contribute to the mass of the nucleus itself.

Thus, the choice highlighting the combination of neutrons and protons accurately reflects the fundamental structure of the nucleus.