Which subatomic particle has the least mass?

• A. Electron
• B. Proton
• C. Neutron
• D. Alpha particle

Answer: (A)

Verified step by step guidance

1. Recall the three main subatomic particles: proton, neutron, and electron, and understand their relative masses.
2. Know that a proton and a neutron have masses close to 1 atomic mass unit (amu), with the neutron being slightly heavier than the proton.
3. Recognize that an electron has a much smaller mass compared to protons and neutrons, approximately 1/1836 of a proton's mass.
4. Understand that an alpha particle consists of 2 protons and 2 neutrons, so its mass is roughly 4 amu, which is much larger than any single subatomic particle.
5. Conclude that among the options given, the electron has the least mass because it is significantly lighter than protons, neutrons, and alpha particles.