Question: what is the lightest subatomic particle in an atom?
Answer: Electron, lightest stable subatomic particle known. ... It carries a negative charge of 1.602176634 × 10−19 coulomb, which is considered the basic unit of electric charge. The rest mass of the electron is 9.1093837015 × 10−31 kg, which is only 1/1,836the mass of a proton.