Which of the following subatomic particles has the smallest mass?

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

Answer: (C)

Verified step by step guidance

1. Recall the basic subatomic particles and their relative masses: electron, proton, neutron, and alpha particle (which is a helium nucleus).
2. Understand that the electron is a fundamental particle with a very small mass compared to nucleons (protons and neutrons).
3. Note that protons and neutrons have masses close to 1 atomic mass unit (amu), while electrons have a mass approximately 1/1836 of a proton.
4. Recognize that an alpha particle consists of 2 protons and 2 neutrons, so its mass is roughly 4 amu, much larger than a single proton or neutron.
5. Conclude that among the given options, the electron has the smallest mass because it is much lighter than protons, neutrons, and alpha particles.