Step-by-step explanation:
The radioactive elements are unstable in nature. To become stable, it emits radiations. They emit alpha rays, gamma rays and beta rays.
It occurs in unstable atomic nuclei.
Radioactive decay: it is the spontaneous breakdown of an unstable atomic nuclei. It is also known as nuclear decay.
For example, the radioactive decay of uranium 238 gives thorium as daughter nuclei along with alpha particles.