Which subatomic particle has the smallest mass?

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

Answer: (D)

Verified step by step guidance

1. Identify the subatomic particles mentioned: alpha particle, proton, neutron, and electron.
2. Recall that an alpha particle is composed of 2 protons and 2 neutrons, so its mass is roughly the sum of these nucleons, making it much heavier than individual protons or neutrons.
3. Understand that protons and neutrons have similar masses, each approximately 1 atomic mass unit (amu).
4. Recognize that electrons are fundamental particles with a mass about 1/1836 that of a proton, making them significantly lighter than protons and neutrons.
5. Conclude that among the given options, the electron has the smallest mass.