Everything about Nuclide totally explained
A
nuclide (from lat.: nucleus) is a nuclear species which is characterized by the number of
protons and
neutrons that every
atomic nucleus of this species contains. It can be used to distinguish
isotopes among nuclei, as well as other properties listed below.
For a short-hand designation of the nuclide, one writes the
mass number (number of
nucleons) in the upper left corner and the
atomic number (number of
protons) in the lower left corner of the chemical symbol: for example, for the most common
isotope of carbon. In earlier years, the mass number was written in the upper right corner. The atomic number may also be omitted, since it's uniquely defined by the
element symbol: for example, . Where needed, the number of neutrons can be written in the lower left corner for clarity: for example, . This is normally omitted, as it can be deduced by subtracting the element number from the mass number.
The various nuclides of a particular
chemical element with equal proton number (atomic number), but different neutron numbers are called
isotopes of this element. Before the term "nuclide" was internationally accepted (ca. 1950), the term "isotope" was also loosely used to describe a nuclear species, for example, a nuclide. Nuclides with equal
mass number but different
atomic number are called
isobars (isobar = equal in weight).
Isotones are nuclides of equal neutron number but different proton numbers.
Nuclear isomers are atomic nuclei of a particular nuclide that have equal proton number and equal mass number, differ in energy content, and are long-lived (for example the two states of shown among the
decay schemes).
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 |
, |
|
| Isotones |
equal neutron number |
, |
|
| Isobars |
equal mass number |
,, |
see beta decay |
| Mirror nuclei |
neutron and proton number exchanged |
, |
| Nuclear isomers |
different energy states |
|
long-lived or stable |
About 270 stable and about 70 unstable (radioactive) nuclei exist in nature. There are three main types of natural radionuclides. Firstly, those whose
half-lives T
1/2 are at least 10% as long as the age of the
earth (4.6×10
9 years). These are remnants of
nucleosynthesis that occurred in stars before the formation of the
solar system. For example, the isotope (T
1/2 = 4.5×10
9 a) of
uranium occurs in nature, but the shorter-lived isotope, (T
1/2 = 0.7 ×10
9 a), is 138 times rarer. The second group consists of isotopes such as (T
1/2 = 1602 a), an isotope of
radium, which are formed in the radioactive decay chains of uranium or thorium. The third group consists of nuclides such as (
radiocarbon) that are made by
cosmic-ray bombardment of other elements. Many more than 1000 nuclides have been artificially produced.
The known nuclides are shown in
charts of the nuclides (see Weblinks)
Further Information
Get more info on 'Nuclide'.
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