Here's why:

* Definition: One electron volt is the amount of energy gained by an electron when it moves through an electric potential difference of one volt.

* Relationship to Joules: 1 eV is equal to 1.602 x 10⁻¹⁹ joules (J).

* Usage: Electron volts are commonly used in atomic and nuclear physics, as well as in fields like particle physics and astrophysics. It's a convenient unit for representing the energies of atoms, electrons, and other small particles.