A table of nuclides or chart of nuclides is a two-dimensional graph in which one axis represents the number of neutrons and the other represents the number of protons in an atomic nucleus. Each point plotted on the graph thus represents the nuclide of a real or hypothetical chemical element. This system of ordering nuclides can offer a greater insight into the characteristics of isotopes than the better-known periodic table, which shows only elements instead of each of their isotopes.
A chart or table of nuclides is a simple map to the nuclear, or radioactive, behaviour of nuclides, as it distinguishes the isotopes of an element. It contrasts with a periodic table, which only maps their chemical behavior, since isotopes of the same element do not differ chemically. Nuclide charts organize isotopes along the X axis by their numbers of neutrons and along the Y axis by their numbers of protons, out to the limits of the neutron and proton drip lines. This representation was first published by Giorgio Fea in 1935, and expanded by Emilio Segrè in 1945 or G. Seaborg. In 1958, Walter Seelmann-Eggebert and Gerda Pfennig published the first edition of the Karlsruhe Nuclide Chart. Its 7th edition was made available in 2006. Today, one finds several nuclide charts, four of them have a wide distribution: the Karlsruhe Nuclide Chart, the Strasbourg Universal Nuclide Chart, the Chart of the Nuclides from the JAEA and the Nuclide Chart from Knolls Atomic Power Laboratory. It has become a basic tool of the nuclear community.
Isotopes are nuclides with the same number of protons but differing numbers of neutrons; that is, they have the same atomic number and are therefore the same chemical element. Isotopes neighbor each other vertically, e.g., carbon-12, carbon-13, carbon-14 or oxygen-15, oxygen-16, oxygen-17.
Isotones are nuclides with the same number of neutrons but differing number of protons. Isotones neighbor each other horizontally. Example: carbon-14, nitrogen-15, oxygen-16 in the sample table above.
Isobars are nuclides with the same number of nucleons, i.e. mass number, but different numbers of protons and different number of neutrons. Isobars neighbor each other diagonally from lower-left to upper-right. Example: carbon-14, nitrogen-14, oxygen-14 in the sample table above.
Isodiaphers are nuclides with the same difference between neutrons and protons (N−Z). Like isobars, they follow diagonal lines, but at right angles to the isobar lines; from upper-left to lower right. Examples: boron-10, carbon-12, nitrogen-14 where N−Z=0; boron-12, carbon-14, nitrogen-16 where N−Z=2.
Beyond the proton drip line along the upper left, nuclides decay by proton emission. Drip lines have only been established for some elements.
The island of stability is a hypothetical region of the table of nuclides that contains isotopes far more stable than other transuranic elements.
There are no stable atoms having an equal number of protons and neutrons in their nuclei with atomic number greater than 20 (i.e. calcium) as can be readily "read" from the chart. Nuclei of greater atomic number require an excess of neutrons for stability.
There are no stable atoms with mass numbers 5 or 8. There are stable atoms with all other mass numbers up to 208 with the exceptions of 147 and 151. (Bismuth-209 was found to be radioactive in 2003, but with a half-life of 1.9×1019 years.)
With the possible exception of the pair tellurium-123 and antimony-123, odd mass numbers are never represented by more than one stable atom. This is because the mass-energy is a convex function of atomic number, so all nuclides on an odd isobar except one have a lower-energy neighbor to which they can decay by beta decay.
There are no stable atoms having atomic number greater than Z=82 (lead), although bismuth (Z=83) is stable for all practical human purposes. Atoms with atomic numbers of 82 and lower all have stable isotopes, with the exceptions of technetium (Z=43) and promethium (Z=61).
Presents the data via four separate charts, each typically with 30 elements. Depending on the browser, no horizontal scrolling is required in window widths of at least 1225 to 1440 pixels (311 kB total HTML download).
Presents the data in a one-dimensional list where the 905 nuclides which are either stable or radioactive with half lives greater than 60 minutes are sorted by their half-life, including specific mass excess and decay-modes, no horizontal scrolling is required (95 kB total HTML download).
Provides both the eight-chart, segmented presentation and the single, contiguous chart. Provides quick-jump hyperlinks to jump between the two. Features expanded introductory text for first-time readers. (588 kB total HTML download).