Which statement about the composition of protons and neutrons is accurate?

Which statement about the composition of protons and neutrons is accurate?

• A. Protons and neutrons are elementary particles.
• B. Protons are made of gluons, neutrons are made of quarks.
• C. Protons and neutrons are made of quarks.
• D. Protons and neutrons are made of leptons.

Answer: (C)

Protons and neutrons are not elementary; they’re made of quarks. In the Standard Model, they are baryons composed of three valence quarks: a proton has two up quarks and one down quark, while a neutron has one up quark and two down quarks. The charges of these quarks add up to give the proton’s charge of +1 and the neutron’s neutral charge, and gluons glue these quarks together via the strong force. Leptons, like electrons, are a different family of particles, so protons and neutrons aren’t made of leptons. This is why the statement that protons and neutrons are made of quarks is the accurate description.

Protons and neutrons are not elementary; they’re made of quarks. In the Standard Model, they are baryons composed of three valence quarks: a proton has two up quarks and one down quark, while a neutron has one up quark and two down quarks. The charges of these quarks add up to give the proton’s charge of +1 and the neutron’s neutral charge, and gluons glue these quarks together via the strong force. Leptons, like electrons, are a different family of particles, so protons and neutrons aren’t made of leptons. This is why the statement that protons and neutrons are made of quarks is the accurate description.