Final answer:
An electron-volt (eV) is a unit of energy defined as the energy given to the charge of an electron when accelerated through a potential difference of 1 V, equal to 1.60×10-19 Joules. It is much smaller than a joule and highly useful in describing atomic and subatomic energy processes.
Step-by-step explanation:
An electron-volt (eV) is a unit of energy on the submicroscopic scale. It's defined as the energy given to a fundamental charge, which is the charge of an electron, accelerated through a potential difference of 1 V. In mathematical terms, 1 eV is calculated as the product of the electron charge (which is approximately 1.60×10-19 Coulombs) and the potential difference (1 Volt), yielding 1 eV = 1.60×10-19 Joules. Therefore, when we look at the options provided, the closest answer is D) an amount of energy much smaller than a joule.
The electron-volt is conveniently used for expressing energy levels in atoms, and in the case of atomic and subatomic particles, where such small amounts of energy occur. For example, it's commonly used in physics to describe the energy levels of electrons within an atom or in describing particle energies. Even though the energy of an electron-volt is quite small when compared to the joule, it is immensely useful in these contexts.