Editing Atomic number (section)

== New elements ==
The quest for new elements is usually described using atomic numbers. As of {{year}}, all elements with atomic numbers 1 to 118 [[Discovery of chemical elements|have been observed]]. The most recent element discovered was number 117 ([[tennessine]]) in 2009. Synthesis of new elements is accomplished by bombarding target atoms of heavy elements with ions, such that the sum of the atomic numbers of the target and ion elements equals the atomic number of the element being created. In general, the [[half-life]] of a [[nuclide]] becomes shorter as atomic number increases,{{cn|date=January 2022}} though [[Extended periodic table|undiscovered nuclides]] with certain "[[magic number (physics)|magic]]" numbers of protons and neutrons may have relatively longer half-lives and comprise an [[island of stability]].

A hypothetical element composed only of neutrons, [[neutronium]], has also been proposed and would have atomic number 0,<ref name='Antropoff 1926'>{{cite journal | last = von Antropoff | first = A. | title = Eine neue Form des periodischen Systems der Elementen | journal = [[Zeitschrift für Angewandte Chemie]] | date = 1926 | volume = 39 | issue = 23 | pages = 722–725 | doi = 10.1002/ange.19260392303| bibcode = 1926AngCh..39..722V |lang=de}}</ref> but has never been observed.