Which subatomic particle has a mass approximately 1 atomic unit and a positive electric charge?

Which subatomic particle has a mass approximately 1 atomic unit and a positive electric charge?

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

Answer: (B)

Mass in atomic mass units is the key idea here. The proton has a mass of about 1.007 amu, which is essentially 1 amu, and it carries a positive electric charge (+1e). Neutrons have a similar mass but carry no charge, so they don’t fit the positive-charge part. Electrons are far lighter—around 0.00055 amu—and are negatively charged. The positron has the same tiny mass as the electron but a positive charge, so it doesn’t match the mass criterion despite having a positive charge. That combination of about 1 amu and a +1 charge points to the proton as the correct particle.

Mass in atomic mass units is the key idea here. The proton has a mass of about 1.007 amu, which is essentially 1 amu, and it carries a positive electric charge (+1e). Neutrons have a similar mass but carry no charge, so they don’t fit the positive-charge part. Electrons are far lighter—around 0.00055 amu—and are negatively charged. The positron has the same tiny mass as the electron but a positive charge, so it doesn’t match the mass criterion despite having a positive charge. That combination of about 1 amu and a +1 charge points to the proton as the correct particle.