Nuclide
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A nuclide (from nucleus, originally from Latin, meaning kernel of a nut) is an atomic species characterized by the specific constitution of
its nucleus, i.e., by its number of protons Z, its number of neutrons N, and its energy state.[1] Thus, all nuclides are atoms which have at
least one electron (though certain ions may be included), but naked nuclei (such as those occurring in cosmic rays and sufficiently hot
plasmas) do not technically qualify for the term (these are instead naked nuclei of various nuclear species(elements)). In short, a nuclide
is an umbrella term for all nuclei with one or more electrons orbiting.
A set of nuclides with equal proton number (atomic number), i.e. of the same chemical element, but different neutron numbers, are called
isotopes of the element. Particular nuclides are still often loosely called "isotopes", but the term "nuclide" is the correct one in general
(i.e. when Z is not fixed).
A set of nuclides with equal mass number A but different atomic number are called isobars (isobar = equal in weight), and isotones are
nuclides of equal neutron number but different proton numbers. The name isotone has been derived from the name isotope to remind
that in the first group of nuclides it is the number of neutrons (n) that is constant, whereas in the second the number of protons (p).[2]
No matter how the IUPAC definition of the atom will develop (at present it is still considered as a neutral entity formed by a nucleus
containing Z>0 protons surrounded by Z electrons), the neutral atoms will always be the “default” for any nuclide. This is so because the
atomic weight, or more precisely: the average relative atomic mass Ar(E) of an element E, is calculated from the relative atomic masses of
its isotopes weighted with their atomic abundances. The relative atomic masses of nuclides in general are also called (relative) “nuclidic
masses” in short. These are the mass data that you find in data bases. Note that such masses always refer to neutral atoms in their
lowest energy state.
There are about 256 nuclides in nature which are so stable that they have never been observed to decay. They occur among the 80
different elements which have one or more stable isotopes. See stable isotope and primordial nuclide.
Nuclear isomers are members of a set of nuclides with equal proton number and equal mass number, but different states of excitation. An
example is the two states of 9943Tc shown among the decay schemes. The most long-lived non-ground-state nuclear isomer is
tantalum-180m, which has a halflife in excess of 1000 trillion years, and has not been observed to decay to tantalum-180.
Unstable nuclides are radioactive and are called radionuclides. Their decay products ('daughter' products) are called radiogenic nuclides.
Designation Characteristics Example Remarks
Isotopes equal proton number 126C,
13
6C
Isotones equal neutron number 136C,
14
7N
Isobars equal mass number 177N,
17
8O,
17
9F see beta decay
Mirror nuclei neutron and proton number exchanged 31H,
3
2He
Nuclear isomers different energy states 9943Tc,
99m
43Tc long-lived or stable
About 256 stable and about 83 unstable (radioactive) nuclides exist naturally on Earth.
Natural radionuclides may be conveniently subdivided into three types. Firstly, those whose half-lives T½ are at least 10% as long as the
age of the earth (4.6×109 years). These are remnants of nucleosynthesis that occurred in stars before the formation of the solar system.
For example, the isotope 238U (T½ = 4.5×109 a) of uranium is still fairly abundant in nature, but the shorter-lived isotope, 235U (T½ = 0.7
×109 a), is 138 times rarer. The second group consists of nuclides such as 226Ra (T½ = 1602 a), an isotope of radium, which are formed
in the radioactive decay chains of uranium or thorium. Some of these nuclides are very short lived, such as isotopes of francium. The third
group consists of nuclides which are continually being made in another fashion, such as 14C (radiocarbon) that are made by cosmic-ray
bombardment of other elements, and promethium which is still being created by neutron bombardment in other stars, and has been
detected there by its spectrum.
More than 3000 nuclides have been artificially produced.
The known nuclides are shown in charts of the nuclides (see external links)
See also
List of Nuclides
Primordial element
Primordial nuclide
Table of nuclides sorted by half-life
Table of nuclides
Isotope geochemistry
Radionuclide
Monoisotopic element
Mononuclidic element
Stable isotope
Nuclide - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Nuclide
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List of elements by stability of isotopes
List of elements by nuclear stability
References
^ nuclide entry (http://goldbook.iupac.org/N04257.html) in the IUPAC Compendium of Chemical Terminology - the Gold Book1.
^ Cohen E.R., Giacomo P. (1987). Symbols, units, nomenclature and fundamental constants in physics. Physica A, 146A, 1-682.
External links
Karlsruhe Nuclide Chart (http://www.karlsruhenuclidechart.net/)
Chart of the nuclides (http://www.nndc.bnl.gov/nudat2/)
NUCLEONICA nuclear science portal (http://www.nucleonica.net)
Details about the nuclides (http://atom.kaeri.re.kr/ton/)
Periodic system with details of the nuclides (http://www.webelements.com/)
Universal Nuclide Chart from Nucleonica (http://www.nucleonica.net/unc.aspx)
Interacive Chart of the nuclides, isotopes and Periodic Table (http://www.yoix.org/elements.html)
The LIVEChart of Nuclides - IAEA (http://www-nds.iaea.org/livechart) in Java (http://www-nds.iaea.org/livechart) or
HTML (http://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html)
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Categories: Isotopes | Nuclear physics
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