Which subatomic particle carries a negative charge and is the lightest in the atom?

• A. Electron
• B. Proton
• C. Neutron
• D. Positron

Answer: (A)

Understanding how atoms are built involves two key properties: electric charge and mass. The particle that is negative and the lightest among those inside an atom is the electron. It carries a negative electric charge, whereas protons carry a positive charge and neutrons have no charge. In terms of mass, the electron is vastly lighter than both protons and neutrons—about 1/1836 of a proton’s mass. A posi tron has a positive charge (it’s the electron’s antiparticle) and the same mass as an electron, so it’s not the one described. So the electron best fits both criteria: negative charge and being the lightest.