29 lines
1.8 KiB
Markdown
29 lines
1.8 KiB
Markdown
---
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title: "Atomic number"
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chunk: 3/3
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source: "https://en.wikipedia.org/wiki/Atomic_number"
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category: "reference"
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tags: "science, encyclopedia"
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date_saved: "2026-05-05T10:51:54.272199+00:00"
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instance: "kb-cron"
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---
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== New elements ==
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The quest for new elements is usually described using atomic numbers. As of 2026, all elements with atomic numbers 1 to 118 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, though undiscovered nuclides with certain "magic" numbers of protons and neutrons may have relatively longer half-lives and comprise an island of stability.
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A hypothetical element composed only of neutrons, neutronium, has also been proposed and would have atomic number 0, but has never been observed.
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== See also ==
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Atomic theory
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Chemical element – Chemical substance not composed of simpler ones
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Effective nuclear charge – Measurement in atomic physics
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Effective atomic number (compounds and mixtures) – Approximate atomic number calculated for materials with many elements
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Even and odd atomic nuclei – Nuclear physics classification method
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History of the periodic table – Development of the table of chemical elements
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List of chemical elements
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Mass number – Number of heavy particles in the atomic nucleus
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Neutron number – Number of neutrons in a nuclide
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Neutron–proton ratio – Ratio of neutrons to protons in an atomic nucleus
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Prout's hypothesis – Early model of the atom that did not account for mass defect
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== References == |