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At least 3,300 nuclides have been experimentally characterized [1] (see List of radioactive nuclides by half-life for the nuclides with decay half-lives less than one hour). A nuclide is defined conventionally as an experimentally examined bound collection of protons and neutrons that either is stable or has an observed decay mode .
This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds.
As the number of protons increases, so does the ratio of neutrons to protons necessary to ensure a stable nucleus (see graph). For example, although the neutron–proton ratio of 3 2 He is 1:2, the neutron–proton ratio of 238 92 U is greater than 3:2. A number of lighter elements have stable nuclides with the ratio 1:1 (Z = N). The nuclide 40 ...
A table or chart of nuclides is a two-dimensional graph of isotopes of the elements, in which one axis represents the number of neutrons (symbol N) and the other represents the number of protons (atomic number, symbol Z) in the atomic nucleus. Each point plotted on the graph thus represents a nuclide of a known or hypothetical chemical element.
Periodic table for looking up element numbers (atomic number) These isotope tables show all of the known isotopes of the chemical elements, arranged with increasing atomic number from left to right and increasing neutron number from top to bottom. Half lives are indicated by the color of each isotope's cell (see color chart in each section).
Two beta-decay stable nuclides exist for odd neutron numbers 1 (2 H and 3 He), 3 (5 He and 6 Li – the former has an extremely short half-life), 5 (9 Be and 10 B), 7 (13 C and 14 N), 55 (97 Mo and 99 Ru), and 85 (145 Nd and 147 Sm); the first four cases involve very light nuclides where odd-odd nuclides are more stable than their surrounding ...
Stable even–even nuclides number as many as three isobars for some mass numbers, and up to seven isotopes for some atomic numbers. Conversely, of the 251 known stable nuclides, only five have both an odd number of protons and odd number of neutrons: hydrogen-2 , lithium-6, boron-10, nitrogen-14, and tantalum-180m.
Proton number Z, also named the atomic number, determines the position of an element in the periodic table. The approximately 3300 known nuclides [7] are commonly represented in a chart with Z and N for its axes and the half-life for radioactive decay indicated for each unstable nuclide (see figure). [8]