Any of the elements of Group 18, which includes helium, neon, argon, krypton, xenon, radon, and element 118. These elements are referred to as "inert" or "noble" because they do not easily form ...
Spontaneous emission of particles or high-energy electromagnetic radiation from the nuclei of unstable atoms. "Radiation" refers to the emissions, and "radioactive source" refers to the source of ...
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