Transuranic elements are elements that have an atomic number greater than 92. Transuranic elements have been synthesised in nuclear reactors or in high-energy particle accelerators. Neptunium and plutonium were the first transuranic elements to be synthesised in 1940 by Glenn Seaborg’s research team in the USA. Uranium 238 is bombarded with neutrons produced by the nuclear fission of U-235. Initially an isotope of uranium (U-239) forms which decays by beta emission to produce neptunium-239. Neptunium-239 decays by beta emission to produce Pu-239.
23892U + 10n 23992U 23993Np + 0 -1e
23993Np 23994Pu + 0-1e
Pu-239 is changed to americium by neutron bombardment.
Americium-241 is used in most house smoke alarms.
Note how mass (shown by the upper superscript numbers) is conserved and how charge (shown by the lower subscript numbers) is conserved.
Always check that a nuclear equation is balanced in the two ways shown in the equation above.
Apart from using neutrons, alpha particles have been used to produce transuranic elements. Thus, curium-242 was produced by alpha bombardment of plutonium.
23894Pu + 42He 24296Cm + 10n
Another method of making transuranic elements is to bombard target nuclei with the nuclei of other elements using particle accelerators. New elements form when the nuclei fuse together. These elements are highly unstable and rapidly decay. Hassium-265 (Z=108) was produced in 1984 by firing Fe-58 nuclei at Pb-208 targets.
20882Pb + 5826Fe 265108Hs + 10n
How are commercial radioisotopes produced
There are only about 50 naturally occurring radioactive isotopes. However, about 2000 radioisotopes have been created. About 20 have found widespread use in medicine and...