Which of the following is the smallest subatomic particle?

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

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the types of subatomic particles involved. The options are electron, neutron, proton, and alpha particle. Electrons, neutrons, and protons are fundamental particles found inside atoms, while an alpha particle is a cluster of two protons and two neutrons.
2. Step 2: Recall the relative masses of these particles. Electrons have a much smaller mass compared to protons and neutrons. Protons and neutrons have roughly the same mass, which is about 1 atomic mass unit (amu).
3. Step 3: Recognize that an alpha particle is composed of multiple nucleons (2 protons + 2 neutrons), so its mass is approximately 4 amu, making it larger than individual protons or neutrons.
4. Step 4: Compare the sizes and masses: electrons are subatomic particles with negligible mass compared to protons and neutrons, making them the smallest among the given options.
5. Step 5: Conclude that the electron is the smallest subatomic particle listed, based on its significantly smaller mass and size relative to protons, neutrons, and alpha particles.