The energy of ionizing radiation is measured in _____________.

The energy of ionizing radiation is best measured in electron volts (eV). This unit specifically describes the energy gained by an electron when it is accelerated through an electric potential difference of one volt. Since ionizing radiation involves particles or photons that can cause ionization in atoms and molecules, the electron volt is particularly useful in measuring their energy levels.

Ionizing radiation, such as photons from X-ray and gamma-ray sources, are often represented in terms of eV because it provides a convenient scale that reflects the energy ranges typically associated with these forms of radiation. For context, 1 eV is equivalent to approximately 1.6 x 10^-19 joules, which indicates how small the energy values commonly associated with ionizing radiation can be.

Other units mentioned, such as joules, rads, and sieverts, serve different purposes. Joules are a general unit of energy but are less practical for the context of ionizing radiation. Rads and sieverts are units of dose and biological effect, respectively, and while they are related to exposure and risk assessment, they do not measure the energy of the radiation itself.