Which three particles are found in the nucleus of an atom?

The nucleus of an atom is composed of two types of particles: protons and neutrons. Protons are positively charged particles that play a crucial role in defining the atomic number of an element, which determines its identity in the periodic table. Neutrons, on the other hand, are neutral particles that contribute to the overall mass of the atom and help stabilize the nucleus by offsetting the repulsive forces between the positively charged protons.

Electrons, while crucial for the overall structure and reactivity of the atom, reside in orbitals surrounding the nucleus rather than in the nucleus itself. Options that include photons or positrons misrepresent the constituents of the nucleus. Quarks are subatomic particles that make up protons and neutrons but are not found in the nucleus as distinct entities. Thus, focusing on protons and neutrons accurately reflects the composition of the atomic nucleus, making the highlighted choice the only correct answer to this question.