What is the term for radiation that is emitted from radioactive materials?

The term for radiation emitted from radioactive materials is indeed radiation itself. Radiation encompasses a wide variety of energy emissions, including alpha particles, beta particles, gamma rays, x-rays, and neutrons, which are all produced by radioactive decay processes. This overarching term includes all forms of ionizing and non-ionizing energy that is released as unstable atomic nuclei transition to a more stable state.

Focusing on the other terms, photons specifically refer to packets of light energy and are a type of electromagnetic radiation. While gamma rays, which are a product of radioactive decay, can be classified as photons, this term does not adequately encompass all types of radiation emitted from radioactive substances. Ions refer to atoms or molecules that have gained or lost one or more electrons, which does not directly describe the emitted radiation itself but rather changes in the atomic structure as a result of interactions with radiation. Electrons are subatomic particles that can be emitted during radioactive decay (beta decay specifically) but do not represent the entirety of the radiation spectrum emitted by radioactive materials.

Thus, the broad and inclusive term "radiation" is used to describe the various forms of energy released during the decay of radioactive materials, making it the most appropriate choice in this context.