Which subatomic particle has a mass of about 1 atomic mass unit and no electric charge?

Which subatomic particle has a mass of about 1 atomic mass unit and no electric charge?

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

Answer: (C)

Think about a particle that weighs about the same as a proton but has no electric charge. That description fits the neutron. Neutrons have a mass close to 1 amu and carry no net charge, so they’re electrically neutral. Protons also weigh about 1 amu but are positively charged, electrons are far lighter and carry a negative charge, and positrons are positively charged particles with the same tiny mass as electrons. So the neutron is the one that matches both clues.

Think about a particle that weighs about the same as a proton but has no electric charge. That description fits the neutron. Neutrons have a mass close to 1 amu and carry no net charge, so they’re electrically neutral. Protons also weigh about 1 amu but are positively charged, electrons are far lighter and carry a negative charge, and positrons are positively charged particles with the same tiny mass as electrons. So the neutron is the one that matches both clues.