Editing Nuclide (section)

==Types of nuclides==
<!--[[File:Island_of_Stability.svg|thumb|right|500px|Stability of nuclides]]-->
Although the words nuclide and isotope are often used interchangeably, being isotopes is actually only one relation between nuclides. The following table names some other relations.
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{| class="wikitable" style="float:left; margin:0em 0em 0em 1em;"
!Designation
!Characteristics
!Example
!Remarks
|- style="height:2em;"
|[[Isotope]]s
|equal proton number ([[atomic number|Z]]<sub>1</sub> = Z<sub>2</sub>)
|{{nuclide|link=yes|Carbon|12}}, {{nuclide|link=yes|Carbon|13}}, {{nuclide|link=yes|Carbon|14}}
| see [[neutron capture]]

|- style="height:2em;"
|[[Isotone]]s
|equal neutron number ([[neutron number|N]]<sub>1</sub> = N<sub>2</sub>)
|{{nuclide|link=yes|Carbon|13}}, {{nuclide|link=yes|Nitrogen|14}}, {{nuclide|link=yes|Oxygen|15}}
| see [[proton capture]]

|- style="height:2em;"
|[[Isobar (nuclide)|Isobars]]
|equal mass number (Z<sub>1</sub> + N<sub>1</sub> = Z<sub>2</sub> + N<sub>2</sub>)
|{{nuclide|link=yes|Nitrogen|17}}, {{nuclide|link=yes|Oxygen|17}}, {{nuclide|link=yes|Fluorine|17}}
|see [[beta decay]]
|- style="height:2em;"
|Isodiaphers
|equal neutron excess (N<sub>1</sub> − Z<sub>1</sub> = N<sub>2</sub> − Z<sub>2</sub>)
|{{nuclide|link=yes|Carbon|13}}, {{nuclide|link=yes|Nitrogen|15}}, {{nuclide|link=yes|Oxygen|17}}
|Examples are isodiaphers with neutron excess 1.<br/>
A nuclide and its [[alpha decay]] product are isodiaphers.<ref name=sharma/>
|- style="height:2em;"
|[[Mirror nuclei]]
|neutron and proton number exchanged<br/>
(Z<sub>1</sub> = N<sub>2</sub> ''and'' Z<sub>2</sub> = N<sub>1</sub>)
| style="text-align: center;" |{{nuclide|link=yes|Hydrogen|3}}, {{nuclide|link=yes|Helium|3}}
| see [[positron emission]]

|- style="height:2em;"
|[[Nuclear isomer]]s
|same proton number ''and'' mass number,<br/>
but with different energy states
| style="text-align: center;" |{{nuclide|link=yes|Technetium|99}}, {{nuclide|link=yes|Technetium|99m}}
|m=metastable (long-lived excited state)
|}
{{Clear|left}}

A set of nuclides with equal proton number ([[atomic number]]), i.e., of the same [[chemical element]] but different [[neutron number]]s, are called [[isotope]]s 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). In similar manner, a set of nuclides with equal [[mass number]] ''A'', but different [[atomic number]], are called [[isobar (nuclide)|isobars]] (isobar = equal in weight), and [[isotone]]s are nuclides of equal neutron number but different proton numbers. Likewise, nuclides with the same neutron excess (''N''&nbsp;−&nbsp;''Z'') are called isodiaphers.<ref name=sharma>{{cite book|last=Sharma|first=B.K.|title=Nuclear and Radiation Chemistry|date=2001 |edition=7th|publisher=Krishna Prakashan Media|isbn=978-81-85842-63-9|page=78}}</ref> The name isoto'''n'''e was derived from the name isoto'''p'''e to emphasize 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).<ref>
{{cite journal
|last=Cohen |first=E. R.
|last2=Giacomo |first2=P.
|year=1987
|title=Symbols, units, nomenclature and fundamental constants in physics
|journal=[[Physica A]]
|volume=146 |issue=1 |pages=1–68
|bibcode=1987PhyA..146....1.
|citeseerx=10.1.1.1012.880
|doi=10.1016/0378-4371(87)90216-0
}}</ref>

See [[Isotope#Notation]] for an explanation of the notation used for different nuclide or isotope types.

[[Nuclear isomer]]s are members of a set of nuclides with equal proton number and equal mass number (thus making them by definition the same isotope), but different states of excitation. An example is the two states of the single isotope {{nuclide|link=yes|Technetium|99}} shown among the [[decay scheme]]s. Each of these two states (technetium-99m and technetium-99) qualifies as a different nuclide, illustrating one way that nuclides may differ from isotopes (an isotope may consist of several different nuclides of different excitation states).

The longest-lived non-[[ground state]] nuclear isomer is the nuclide [[tantalum-180m]] ({{nuclide|link=yes|Tantalum|180m}}), which has a [[half-life]] in excess of 1,000&nbsp;trillion years. This nuclide occurs primordially, and has never been observed to decay to the ground state. (In contrast, the ground state nuclide tantalum-180 does not occur primordially, since it decays with a half life of only 8&nbsp;hours to <sup>180</sup>Hf (86%) or <sup>180</sup>W (14%).)

There are 251&nbsp;nuclides in nature that have never been observed to decay. They occur among the 80 different elements that have one or more stable isotopes. See [[stable nuclide]] and [[primordial nuclide]]. Unstable nuclides are [[radioactivity|radioactive]] and are called [[radionuclide]]s. Their [[decay product]]s ('daughter' products) are called [[radiogenic nuclide]]s.