Which positively charged subatomic particle is composed of two up quarks and one down quark and is found in atomic nuclei?

Which positively charged subatomic particle is composed of two up quarks and one down quark and is found in atomic nuclei?

• A. Neutrons
• B. Positrons
• C. Electrons
• D. Protons

Answer: (D)

Quark composition determines the charge of nucleons. A proton is made of two up quarks and one down quark. Up quarks carry +2/3 each, down quarks carry -1/3. So the total is +2/3 + +2/3 + (-1/3) = +1, giving a positive charge. Neutrons, in contrast, are udd and sum to 0, electrons are negative and outside the nucleus, and positrons are antiparticles of electrons. The described particle is the proton, the positively charged one found in atomic nuclei.

Quark composition determines the charge of nucleons. A proton is made of two up quarks and one down quark. Up quarks carry +2/3 each, down quarks carry -1/3. So the total is +2/3 + +2/3 + (-1/3) = +1, giving a positive charge. Neutrons, in contrast, are udd and sum to 0, electrons are negative and outside the nucleus, and positrons are antiparticles of electrons. The described particle is the proton, the positively charged one found in atomic nuclei.