Which of the following subatomic particles has the smallest mass?

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

Answer: (C)

Verified step by step guidance

1. Recall the basic properties of subatomic particles: protons, neutrons, and electrons are fundamental components of atoms, while an alpha particle is a cluster of two protons and two neutrons.
2. Understand that the mass of a proton and a neutron are approximately equal, each about 1 atomic mass unit (amu), which is roughly 1.67 \times 10^{-27} kg.
3. Recognize that an electron has a much smaller mass compared to protons and neutrons, approximately 9.11 \times 10^{-31} kg, which is about 1/1836 the mass of a proton.
4. Note that an alpha particle, being composed of two protons and two neutrons, has a mass roughly four times that of a proton or neutron, making it much heavier than an electron.
5. Conclude that among the given options, the electron has the smallest mass because it is significantly lighter than protons, neutrons, and alpha particles.