Which particle is neutral and has a mass close to that of a proton?

Which particle is neutral and has a mass close to that of a proton?

• A. Electron
• B. Positron
• C. Neutron
• D. Proton

Answer: (C)

Think about particles by their charge and their mass. The neutral particle with a mass close to a proton is the neutron. Neutrons have no electric charge, and their mass is about 1 atomic mass unit—essentially the same as a proton. In contrast, electrons and positrons are much lighter (about 1/1836 of a proton’s mass) and carry opposite charges, negative for the electron and positive for the positron. The proton itself has a positive charge, similar in mass to the neutron, but since it is charged, it doesn’t fit the description.

Think about particles by their charge and their mass. The neutral particle with a mass close to a proton is the neutron. Neutrons have no electric charge, and their mass is about 1 atomic mass unit—essentially the same as a proton. In contrast, electrons and positrons are much lighter (about 1/1836 of a proton’s mass) and carry opposite charges, negative for the electron and positive for the positron. The proton itself has a positive charge, similar in mass to the neutron, but since it is charged, it doesn’t fit the description.