* Unstable Nucleus: The nucleus of a radioisotope contains an imbalance of protons and neutrons, making it unstable. This imbalance causes the nucleus to undergo radioactive decay.

* Constant Rate of Decay: Radioactive decay occurs at a constant rate, following a process called half-life. Half-life is the time it takes for half of the radioactive atoms in a sample to decay.

* Breakdown: During radioactive decay, the unstable nucleus emits particles (like alpha, beta, or gamma radiation) to become more stable. This process can result in the formation of a different element.

Examples of radioisotopes:

* Carbon-14: Used for radiocarbon dating

* Uranium-235: Used in nuclear power plants

* Iodine-131: Used in medical treatments

* Cobalt-60: Used in cancer therapy

Key takeaway: Radioisotopes are unstable isotopes that decay at a constant rate, emitting radiation in the process.