Which subatomic particle has the smallest mass?

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

Answer: (B)

Verified step by step guidance

1. Recall the three main subatomic particles: protons, neutrons, and electrons, and understand that an alpha particle is a cluster of 2 protons and 2 neutrons.
2. Identify the approximate masses of each particle: protons and neutrons have masses close to 1 atomic mass unit (amu), while electrons have a much smaller mass.
3. Recognize that the mass of an electron is about 1/1836 that of a proton or neutron, making it significantly lighter.
4. Understand that an alpha particle, being composed of 2 protons and 2 neutrons, has a mass roughly 4 times that of a proton or neutron, so it is much heavier than any single subatomic particle.
5. Conclude that among the options given, the electron has the smallest mass.