1. Any of a series of radioactive chemical elements with atomic numbers from 89 (actinium) to 103 (lawrencium), characterized by filling the 5f electron shell.
Usage: chemistry; technical

Examples

• Uranium and plutonium are actinides used in nuclear energy.
• The actinide series includes some of the heaviest known elements.
• Actinides are typically found in the bottom row of the periodic table.
• Many actinides are highly radioactive and require careful handling.
• Scientists study actinide chemistry to understand nuclear reactions.