What is an electron volt?

What is an electron volt?

• A. The energy required to remove one electron from an atom
• B. The energy gained by an electron when accelerated through a potential difference of two volts
• C. The energy gained by a proton when accelerated through a potential difference of one volt
• D. The energy gained by an electron when accelerated through a potential difference of one volt

Answer: (D)

An electron volt is the amount of energy gained by a single electron when it moves through a potential difference of one volt. Since energy change is qΔV and the electron carries a charge equal to the elementary charge e, this energy is e × 1 V, which is about 1.602×10^-19 joules. This unit is handy because atomic and subatomic energies are typically in the eV range. If you moved the electron through two volts, you’d gain about 2 eV of energy; ionization energy is a different concept, referring to the energy needed to remove an electron from an atom. The energy gained by a proton crossing 1 V would be the same magnitude in joules for the same potential difference, but the term electron volt is defined specifically with respect to the electron’s charge, so the standard definition uses an electron.

An electron volt is the amount of energy gained by a single electron when it moves through a potential difference of one volt. Since energy change is qΔV and the electron carries a charge equal to the elementary charge e, this energy is e × 1 V, which is about 1.602×10^-19 joules. This unit is handy because atomic and subatomic energies are typically in the eV range. If you moved the electron through two volts, you’d gain about 2 eV of energy; ionization energy is a different concept, referring to the energy needed to remove an electron from an atom. The energy gained by a proton crossing 1 V would be the same magnitude in joules for the same potential difference, but the term electron volt is defined specifically with respect to the electron’s charge, so the standard definition uses an electron.