Characteristics and history
Americium, in its most stable form, has an atomic mass of 243. Americium was discovered by Humans on Earth's North American continent for the first time by scientists working in the United States in the year 1945. This element is part of the actinide series of heavy elements, and was named for Earth's continents of North and South America. (ST reference: Star Fleet Medical Reference Manual)
- The Star Fleet Medical Reference Manual used the alternate spelling "americum" for this element.