QUICK REFERENCE
- Symbol: Am
- Atomic Number: 95
- Atomic Weight: [243]
- Element Classification: Actinide
- Discovered By: Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, and Albert Ghiorso
- Discovery Date: 1944
- Name Origin: Named after America, as it is a synthetic element that was discovered in the United States
- Density(g/cc): 13.69
- Melting Point: 1176°C
- Boiling Point: 2607°C (estimated)
- Appearance: Silvery-white, radioactive metal
- Atomic Radius(pm): 173 (estimated)
Discovery
Americium was discovered in 1944 by a research team led by Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, and Albert Ghiorso at the Metallurgical Laboratory (now Argonne National Laboratory) at the University of Chicago as part of the Manhattan Project. The team produced americium by bombarding plutonium-239 with neutrons, resulting in plutonium-240, which then captured another neutron to become plutonium-241. Plutonium-241 underwent beta decay to form americium-241. The element was named americium after the Americas, following the tradition of naming elements to honor geographical locations.
Relation to Other Elements
Americium is a member of the actinide series, which are characterized by their f-orbital electron configurations and radioactive properties. It is similar to other actinides in terms of its chemical behavior and multiple oxidation states, with +3 being the most stable and common in solutions. Americium-241, one of its most significant isotopes, is a major source of alpha particles and is used in smoke detectors and as a neutron source.
Natural Occurrence
Americium does not occur naturally in any significant amount and is primarily produced in nuclear reactors through the neutron bombardment of plutonium.
Uses
Americium has specialized uses, mainly in commercial and scientific applications:
- Smoke Detectors: Americium-241 is used in many household smoke detectors as a source of ionizing radiation. The alpha particles emitted by americium ionize air molecules, allowing the air to conduct electricity. In the presence of smoke, this conductivity decreases, triggering the alarm.
- Neutron Sources: Americium-241, combined with beryllium, is used as a source of neutrons in various scientific and industrial instruments.
- Radioisotope Thermoelectric Generators (RTGs): While less common than plutonium-238, americium-241 has been considered as a potential fuel for RTGs, especially for space missions.
The discovery of americium expanded the understanding of synthetic elements and their potential uses beyond purely scientific research, demonstrating practical applications, particularly in safety devices like smoke detectors.