Amercium

Part of speech: noun

Definitions

1. A synthetic element with atomic number 95, used in certain scientific applications and nuclear reactors
2. A man-made radioactive element, typically categorized as an actinide, and known for its applications in smoke detectors
3. An artificial element produced in nuclear reactions, notable for its use in research and industry, particularly in isotope studies

Etymology: Americium is the element you mean; "amercium" is a misspelling. Glenn Seaborg's team at the University of Chicago first produced it in 1944, and they gave it a name that deliberately echoed the element directly above it in the periodic table. Europium had been named after Europe, so the new element was named after the Americas. Seaborg later recalled that the team jokingly considered "pandemonium" before settling on the more sober choice. The name builds on "America," which derives from the Latinized form of Amerigo Vespucci's first name, "Americus." The discovery was announced in 1945, and the element's name has been used ever since, mainly in its isotope americium-241, which is found in many household smoke detectors.