What is an electron volt (eV)?
By definition, it is the amount of energy gained (or lost) by the charge of a single electron moved across an electric potential difference of one volt. Thus it is 1 volt (1 joule per coulomb, 1 J/C) multiplied by the negative of the electron charge (−1 e, or −1.602176565(35)×10−19 C). Therefore, one electron volt is equal to 1.602176565(35)×10−19 J.