Final answer:
Radioactive decay is the spontaneous change of an unstable nuclide into another. It occurs when the daughter nuclide lies closer to the band of stability than the parent nuclide. The radiation produced during this decay leads to the transformation of a radioactive material into something else.
Step-by-step explanation:
Radioactive decay is the spontaneous change of an unstable nuclide into another. The unstable nuclide, called the parent nuclide, undergoes decay and transforms into a daughter nuclide. This transformation occurs because the daughter nuclide lies closer to the band of stability than the parent nuclide. The radiation produced during radioactive decay can vary, but it ultimately leads to the conversion of a radioactive material into something else.