Which statement defines radioactive materials?

Which statement defines radioactive materials?

• A. Any substance that spontaneously emits ionizing radiation
• B. They are all solids, never gases
• C. They are always safe
• D. They are inert

Answer: (A)

Radioactive materials are defined by their spontaneous emission of ionizing radiation. This means they contain unstable nuclei that decay without any external trigger, releasing particles or radiation such as alpha, beta, gamma rays, or neutrons. The hazard comes from this emission, which can ionize atoms in living tissue and cause damage. They can be solids, liquids, or gases (for example, a radioactive gas like radon exists alongside solid radioactive materials like uranium ore), so the state of matter does not define radioactivity. Statements claiming they are always solids, always safe, or inert are incorrect because radioactivity hinges on spontaneous decay and emission, not on appearance or inertness.

Radioactive materials are defined by their spontaneous emission of ionizing radiation. This means they contain unstable nuclei that decay without any external trigger, releasing particles or radiation such as alpha, beta, gamma rays, or neutrons. The hazard comes from this emission, which can ionize atoms in living tissue and cause damage. They can be solids, liquids, or gases (for example, a radioactive gas like radon exists alongside solid radioactive materials like uranium ore), so the state of matter does not define radioactivity. Statements claiming they are always solids, always safe, or inert are incorrect because radioactivity hinges on spontaneous decay and emission, not on appearance or inertness.