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Isotopes

Definition of terms as well as properties and data of the individual isotopes and nuclides.

 

 Isotopes

The different atomic nuclei (nuclides) of a chemical element are referred to as isotopes:

The isotopes of the element have the same atomic number (number of protons in the atomic nucleus = atomic number) and differ in the number of neutrons and thus also in the atomic mass and atomic volume.

Isotopes show broadly similar chemical reactions and can have different spins, magnetic moments, and other physical properties.

The isotopes are usually denoted by the mass number, e.g. Helium-4; He-4; 4He.

The terms isotopes and nuclides are largely used synonymously, with nuclides more generally (regardless of the chemical element considered) denoting a specific type of atomic nucleus.

 

Glossary: Isotopes

* Isobar:
Nuclear isobars are nuclides of different chemical elements with the same number of nucleons A (rounded mass number), but different numbers of protons Z and neutrons N in the atomic nucleus. In short: different nuclides of equal mass number.

* Isomeric transition:
The spontaneous transition of an atomic nucleus from a metastable excited state to a less excited state or to the ground state.

* Isotone:
Isotopes or nuclides with the same number of neutrons but different atomic numbers.

* Isotope effect:
Due to the different physical properties of two isotopes, they also differ more or less in their chemical properties.

* Isotopic composition:
The proportions of each isotope in a compound. See also: calculation form for the isotopic composition of a compound.

* Isotopic enrichment:
Any chemical or technical process that increases the proportion of a specific isotope in a mixture of isotopes.

* Isotopic mass:
The atomic mass of the considered isotope.

* Isotopic shift:
Isotope shift is a physical effect that manifests itself in the fact that the spectral lines in the atomic spectra of different isotopes of the same element are shifted relative to each other. The reasons for this are differences in the mass, volume or magnetic moment of the atomic nucleus, which lead to slight changes in the electron shells of the atoms and thus to the shifting or splitting of spectral lines.

* Isotopologue:
Isotopologues are chemical compounds whose molecules differ in isotopic composition.

* Metastable state:
If the internal energy of an isotope is increased compared to the ground state (excited state), then the atomic nucleus is in a metabile state and is referred to as a nuclear isomer (see this term). The return to the ground state takes place with the release of energy.

* Monoisotopes:
The 26 chemical elements that have only one stable isotope (nuclide) are called monoisotopic elements; In detail, these are the following basic materials:

* Mononuclidic element:
Chemical elements of which only a single stable isotope occurs in nature are referred to as mononuclidic or monotopic elements.

* Nuclear isomer:
Excited state of a specific isotope whose internal energy differs from the ground state. labeling of the isotope with a trailing m for metastable (e.g. Eu-152m); if there are several core isomers, the m is followed by an additional number (e.g. Eu-152m1, Eu-152m2).

* Primordial:
Isotopes that existed in their present form before the earth was formed are called primordial isotopes or primordial nuclides.

* Radioisotopes:
Unstable isotopes or nuclides of chemical elements that decay while emitting radioactive radiation.

 

General information about the isotopes

The term isotope comes from the fact that the isotopes of an element are in the same place on the periodic table. The name was coined by Frederick Soddy, who received the Nobel Prize in Chemistry in 1921 for his work and findings in the field of isotopes and radionuclides. The term isotope predates the term nuclide, which generally means type of atom. Isotope is therefore still often used in the sense of nuclide, that is, even when we are not just talking about atoms of one and the same element. Nuclide charts provide a visual representation of all isotopes.

Several isotopes have been detected for every known element (the exception is oganesson, which was only artificially produced in 2006). There are around 3300 known nuclides in total. About 245 of these are stable. All the others are unstable, which means that their atoms change into other atoms after a longer or shorter period of time due to radioactive decay. For some nuclides previously considered stable, this time is so long that their decay has only recently been discovered or is still being sought in experiments.

Tin has the most natural isotopes with 10 isotopes, followed by xenon with 9 natural isotopes, 8 of which are stable. Elements that consist of only one natural isotope, on the other hand, are called monotopic elements; this has exactly one primordial isotope.

 

References:

[1] - NN:
Isotopes.
IUPAC Gold Book.

 


Category: Chemical Elements

Last update: 23 November 2022



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