Protons and neutrons are formed from a combination of smaller particles. What are these particles called?

• A. Quarks
• B. Leptons
• C. Bosons
• D. Photons

Answer: (A)

The essential idea is that protons and neutrons are composed of quarks, the fundamental building blocks of matter in the Standard Model. Protons and neutrons are baryons, each made of three quarks bound together by gluons, with the proton consisting of two up quarks and one down quark and the neutron of two down quarks and one up quark. Leptons, like electrons and neutrinos, are separate fundamental particles that do not combine to form nucleons. Bosons are force carriers (such as photons and gluons); they mediate interactions rather than serving as the internal constituents of protons or neutrons. So the particles that actually form protons and neutrons are quarks.