What is the actinide series?

The actinide series contains elements with filling 5f electron shells and includes well-known radioactive elements such as uranium and plutonium. Their chemistry is important in nuclear energy, weapons history, and scientific research. Uranium was isolated as an element in the late 18th century, but its nuclear importance emerged in the 20th century with discoveries in radioactivity and fission. Several actinides beyond uranium are synthetic and do not occur naturally in significant amounts. Because many are highly radioactive, they require careful handling and special facilities.