The subatomic particle with the least mass is the electron. Here's why:
1. Electrons are negatively charged particles found outside the nucleus of an atom.
2. Protons and neutrons are located in the nucleus of an atom. Protons have a positive charge, while neutrons are neutral.
3. Compared to protons and neutrons, electrons have a significantly smaller mass. In fact, the mass of an electron is approximately 1/1836 times the mass of a proton.
4. Due to their tiny mass, electrons contribute very little to the overall mass of an atom. The mass of an atom is mainly determined by the protons and neutrons in the nucleus.
Therefore, the electron is the subatomic particle with the least mass in an atom.
