Dubnium
Dubnium is a synthetic, radioactive chemical element with atomic number 105. It is a transactinide in group 5 of the periodic table.
Atomic number: The number of protons in an atom's nucleus, which determines its chemical element. Dubnium's 105 protons define its identity as element 105.
Fusion-evaporation reaction: A nuclear reaction in which colliding nuclei fuse and the excited product ejects particles, often neutrons. Dubnium atoms have been produced by fusing heavy target nuclei with accelerated projectiles.
Joint Institute for Nuclear Research: A research center in Dubna, Russia, established jointly by participating countries in 1956. The institute's team reported producing element 105 in experiments beginning in 1968.
Tantalum: A dense, corrosion-resistant transition metal with atomic number 73 and group 5 membership. Tantalum is a stable, familiar group 5 element against which dubnium's chemistry is compared.
Periodic table: A tabular arrangement of chemical elements ordered by atomic number and recurring chemical properties. Its position places dubnium in group 5 and period 7.
Dubnium-268: A radioactive isotope of dubnium with mass number 268. This isotope is among the longer-lived dubnium nuclides and supports chemical experiments.
Lawrence Berkeley National Laboratory: A United States national laboratory in Berkeley, California, founded in 1931. Its researchers reported independent evidence for element 105 in 1970.
Niobium: A transition metal with atomic number 41, used in alloys and superconducting materials. Its group 5 chemistry supplies a lighter analogue for dubnium's expected behavior.
Transactinide element: A chemical element with atomic number greater than 103, beginning with rutherfordium. Dubnium belongs to this region of exceptionally heavy synthetic elements.
Alpha decay: A radioactive decay process in which a nucleus emits a helium-4 nucleus. Alpha-decay chains help identify dubnium atoms and their daughter nuclides.