锕 (ā) is a chemical element with the symbol Ac and atomic number 89. It is part of the actinide series in the periodic table and is a soft, silvery-white metal. Found in trace amounts in uranium and thorium ores, it is radioactive and has no stable isotopes. Discovered in 1940 by Glenn T. Seaborg and his team,锕 is primarily used in scientific research and has applications in nuclear reactors. Due to its radioactivity, it must be handled with care, and its use is limited to specialized fields.