What is the difference between the three isotopes of carbon

Isotopes are nuclides (types of atoms) with the same atomic number but different mass numbers. The name (Greek ισο [iso] - same, τόπος [topos] - place) comes from the fact that isotopes of one and the same element are in the same place in the periodic table. However, they appear separately in the nuclide map. So isotopes contain the same number of protons in their atomic nuclei, but different numbers of neutrons.

The term isotope was coined by Frederick Soddy, who received the Nobel Prize in Chemistry in 1921 for his work and knowledge in the field of isotopes and radioactive elements.

As a rule, every naturally occurring element has one or a few stable isotopes, while its remaining isotopes are radioactive (that is, unstable) and sooner or later decay. However, there are also elements in which all isotopes are unstable.

Notation for isotopes

In order to identify different isotopes of an element, the mass number is added to the left above the element symbol. Optionally, the atomic number can be specified on the left below the element symbol, provided that it - z. B. in nuclear reactions - of interest is:

In the running text, on the other hand, the mass number is often simply appended to the element name with a hyphen. So z. B. "Uranium-235" or "Carbon-14", as this corresponds to the way of speaking and no knowledge of the element symbols is necessary.

There are separate names and individual element symbols for the three hydrogen isotopes:

  • The 1H isotope, which is by far the most common isotope, is also called Protium or light hydrogen designated.
  • The 2H isotope is also called deuterium or heavy hydrogen designated. Element symbol: D.
  • The 3H isotope is also called tritium or super heavy hydrogen designated. Element symbol: T.

Occurs in the designation m on (e.g. 16m1N), this means a core isomer. The number after that m is a numbering if several core isomers occur.

Stable isotopes

With 10 stable isotopes, tin has the most naturally occurring isotopes. There is only one stable isotope of 22 so-called pure elements. Such elements are also called anisotopic designated. These are: beryllium, fluorine, sodium, aluminum, phosphorus, scandium, manganese, cobalt, arsenic, yttrium, niobium, rhodium, iodine, cesium, praseodymium, terbium, holmium, thulium, gold.

Although thorium only has one natural isotope, it is not stable. The half-life is 1.4 · 1010 Years. In some textbooks, like bismuth, it is listed as a pure element. According to recent studies, the isotope of bismuth, which was previously considered stable, is an alpha emitter with an extremely long half-life (1.9 · 1019 Years).

Most famous isotopes

A well-known isotope is the radioactive one14C, which is used to determine the age of organic materials (archeology) (radiocarbon method). Carbon (C) is mainly in the stable isotopes 12C and 13C before.

To investigate paleo temperatures, the ratio of two of the stable oxygen isotopes, 18O and 16O used.

The isotope 235U is enriched from natural uranium and used as fuel in nuclear power plants or, more enriched, in nuclear weapons. Has the same usage 239Pooh This is used in most nuclear weapons today, as it can be obtained from spent nuclear reactor fuel without an enrichment process.

238Because of its radioactive decay heat, Pu is used in space travel to generate electricity in radioisotope generators when solar cells can no longer be used at great distances from the sun.

Chemical reactions with isotopes

In their chemical reactions, isotopes of the same element differ only slightly. An example is the electrolysis of water, in which preferably water with the normal 1H reacts and is broken down into hydrogen and oxygen while having water molecules 2Enrich H (deuterium, heavy hydrogen) in the residual water. The reason for this is the different zero point energies of the isotopes.

This difference in chemical reactivity is particularly pronounced in the case of hydrogen / deuterium due to the large relative mass difference; for most of the other elements these effects are many times weaker.

Isotopes in analytics

(See alsoIsotope investigation)

At high resolution, different isotopes of an element can also be differentiated on their spectral lines (isotope shift).

The isotopic composition in a sample is usually determined with a mass spectrometer, in the case of trace isotopes with accelerator mass spectrometry.

Radioactive isotopes can often also be detected based on their radioactivity.

Isotopes also play a role in NMR spectroscopy. For example, in the NMR spectroscopy of organic compounds, the 13C isotope spectroscoped because it is in contrast to 12C has a detectable nuclear spin.

Isotopes are also used in the elucidation of reaction mechanisms or metabolisms with the help of so-called isotope labeling.

The isotopic composition of water is different and characteristic in different places in the world. These differences make it possible to check the declaration of the place of origin for foods such as wine or cheese.

The investigation of certain isotope patterns (in particular 13C isotope patterns) in organic molecules is known as isotopomer analysis. Among other things, it allows the determination of intracellular material flows in living cells. In addition, the analysis of 13C /12C-, 15N /14N and 34S /32S-ratios are widespread in ecology today. Fractionation can be used to track material flows in food webs or to determine the trophic levels of individual species.

See also

Categories: Nuclear Technology | Nuclide | Nuclear chemistry