A radioactive element is a type of chemical element that has an unstable nucleus, causing it to emit radiation in the form of particles or electromagnetic waves. This process, known as radioactive decay, can transform the element into a different element or isotope over time. Common examples of radioactive elements include uranium, radium, and plutonium. Radioactive elements are used in various applications, such as in nuclear power generation, medical treatments like radiation therapy, and in scientific research. While they can provide significant benefits, their radioactivity also poses health risks, necessitating careful handling and safety measures to protect people and the environment.