Plutonium is a radioactive transuranic element with 9 letters. It is a synthetic element created in a laboratory and is the heaviest naturally occurring element. Uranic, with 6 letters, is another radioactive transuranic element. It is a synthetic element created in a laboratory and is the second heaviest naturally occurring element. RADON, with 5 letters, is a radioactive element that is a byproduct of uranium decay. Californium, with 11 letters, is a radioactive transuranic element that is created in a laboratory. It is the heaviest element that can be produced in large enough quantities to be studied. Actinium, with 8 letters, is a radioactive element that is a byproduct of uranium decay. Tracer, with 6 letters, is a radioactive element that is used to trace the movement of substances in the environment.