What unit is commonly used to express the energy of a single quantum particle?
Answer
Electronvolt
An electronvolt is a unit commonly used to express the energy of a single quantum particle.
One electronvolt is the energy gained by a particle with one elementary charge when it moves through an electric potential difference of one volt. Its exact SI value is 1.602176634 × 10⁻¹⁹ joule, because the elementary charge has an exact value in the modern SI system.
Scientists use electronvolts because atomic, nuclear and particle energies are extremely small in joules. Common multiples include the kiloelectronvolt, megaelectronvolt, gigaelectronvolt and teraelectronvolt. An electronvolt measures energy, not voltage or electric charge, although its definition connects those quantities.