Transuranium element

A chemical element with an atomic number greater than uranium’s 92. All transuranium elements are radioactive, and most are made artificially.

Nuclear transmutation: The conversion of one nuclide into another through a change in its nucleus. Nuclear reactions create transuranium elements by changing the proton count of target atoms.
Atomic number: The number of protons in an atom’s nucleus, which defines its chemical element. The boundary is exact: transuranium elements have atomic numbers above 92.
Edwin McMillan: An American physicist who co-discovered neptunium, the first transuranium element identified. His 1940 work established that elements beyond uranium could be produced and detected.
Plutonium-239: A fissile plutonium isotope produced in nuclear reactors and used as nuclear fuel and weapon material. It is a transuranium isotope with major roles in reactor fuel cycles and nuclear arsenals.
Flerovium: A synthetic element with atomic number 114 and a very short-lived known isotope range. Its measured properties help test predictions about shell stabilization in superheavy nuclei.
Neutron capture: A nuclear reaction in which an atomic nucleus absorbs a neutron. Successive neutron captures can build heavier nuclei, especially in reactors and stellar explosions.
Isotope: One of several nuclides of an element, distinguished by its number of neutrons. Each transuranium element can have isotopes with different masses and decay rates.
Glenn T. Seaborg: An American chemist who helped discover several transuranium elements and proposed the actinide concept. His discoveries and periodic-table reorganization shaped the expanding transuranium series.
Americium-241: A radioactive isotope of americium that emits alpha particles and gamma rays. Its radiation makes it useful in ionization smoke detectors and industrial gauges.
Ogannesson: A synthetic element with atomic number 118, the heaviest element currently named. Its behavior may depart sharply from ordinary noble-gas chemistry.

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