Radionuclides

radionuclides are "Versions" of chemical elements that are not stable, or in other words, are susceptible to undergoing radioactive decay.

---

Other /More definition:
Radionuclides are Elements that undergo a process of natural decay. As Radionuclides decay, they emit radiation in the form of alpha or beta particles and gamma photons. Radiation can cause adverse health effects, such as cancer, so limits are placed on radionuclide concentrations in drinking water.

---

Other /More definition:
Radionuclides are any man-made or natural element that emits radiation and that may cause cancer after many years of exposure through drinking water.