Americium

Americium is a radioactive metallic chemical element with atomic number 95. Its isotopes are produced mainly in nuclear reactors, and americium-241 is used in smoke detectors and industrial gauges.

Alpha decay: Radioactive decay in which an atomic nucleus emits a helium-4 nucleus. Americium-241 emits alpha particles that ionize air inside smoke detectors.
Smoke detector: A device that detects smoke and warns of a possible fire. Americium-241 powers the ionization type, one major smoke-detector design.
Glenn T. Seaborg: An American chemist who helped discover several transuranium elements and developed the actinide concept. He led the team that identified americium in 1944.
Atomic number: The number of protons in an atom’s nucleus, which determines its chemical element. Americium’s 95 protons distinguish it from every other element.
Americium-243: A radioactive americium isotope with a half-life of about 7,370 years, formed in nuclear reactors. Its long-lived decay helps account for americium’s persistence in spent nuclear fuel.
Thickness gauge: An instrument that measures material thickness by monitoring radiation transmitted through or reflected from it. Americium-241 can serve as a radiation source in gauges for thin materials.
Albert Ghiorso: An American nuclear chemist who co-discovered multiple transuranium elements using particle accelerators. He contributed to the experiments that produced and identified americium.
Actinide: A member of the metallic element series from actinium through lawrencium, characterized by filling 5f orbitals. Americium is an actinide with chemistry shaped by its 5f electrons.
Neutron capture: A nuclear reaction in which an atomic nucleus absorbs a neutron. Repeated neutron capture in reactors produces heavier americium isotopes.
Nuclear density gauge: A portable instrument that estimates a material’s density from its interaction with radiation. Americium-241 appears in some sources used to measure soil and construction materials.

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